Affinity guided isolation, structure elucidation and total synthesis of laetirobin a and its analogue synthesis for therapeutic development 1 4

Appendix 1
Experimental Section
Appendix 1

Experimental Section
Appendix 1
174

Experimental Section
General Remarks
Chemicals and working techniques
Unless otherwise stated, all reagents were obtained from Acros, Aldrich, Alfa Aesar, Fluka,
Merck or TCI America and used without further purification. Commercial anhydrous solvents
were used throughout and transferred under an argon atmosphere. Additionally, DCM was
dried by distillation over CaH
2
, and THF was dried by distillation over sodium benzophenone
ketyl. Absolute triethylamine and diisoproylamine were distilled over CaH
2
prior to use. All
reactions were performed under argon atmosphere and stirred magnetically in oven-dried
glassware fitted with rubber septa. Inorganic salts and acids were used in aqueous solution
and are reported in % w/v.
NMR spectroscopy
All spectra were measured on a Bruker Avance ACF 300 or Bruker Avance AMX 500
spectrometer. The Bruker Advance 300 spectrometer operated at 300 MHz for the
1
H and 75
MHz for

13
C nuclei, respectively. The Bruker Advance 500 spectrometer operated at 500
MHz for the
1
H and 125 MHz for
13
C nuclei, respectively. Spectra were recorded at 295 K in
CDCl
3
unless noted otherwise. Chemical shifts are calibrated to the residual proton and
carbon resonances of the solvents: CDCl
3
(δ
H
= 7.26 ppm, δ
C
= 77.0 ppm). Data are reported
as follow: chemical shift (multiplicity: s = singlet, d = doublet, t = triplet, dd = doublet of
doublet, m = multiplet, b = broadened, J = coupling constant (Hz), integration).
Experimental Section
175
Mass spectrometry
Low resolution mass spectral analyses were recorded on Finnigan LCQ (ESI ionisation
source). High resolution mass spectral analyses were recorded on Finnigan MAT95XL. The
used mass spectrometric ionisation sources were electron impact (EI) and electrospray
ionisation (ESI). High resolution mass (HRMS) analyses were referenced against
perfluorokerosene. Some of the mass spectra were measured on a Shimadzu ESI-TOF. Low
resolution mass is reported as follow: ionisation source
ionisation mode
: found mass (percent of

adduct). High resolution mass (HRMS) is reported as follow: (ionisation source) found mass
[calcd. [related species] of calculated mass for formula of related species].
Infrared spectroscopy
FT-IR spectra were recorded on a Fourier Transform infrared spectrometer model IR Prestige-
21 (Shimadzu). Solid or crystalline samples were pulverized with potassium bromide (KBr)
and percent transmittance (T%) was measured. The percent transmittance (T%) of liquid
samples or oils were measured in film between sodium chloride (NaCl) discs. Absorption
band frequencies are reported in cm
-1
.
Chromatographic methods
Analytical thin layer chromatography (TLC) was performed on pre-coated with silica gel 60
F
254
glass plates (Merck). The compounds were visualised by UV
254
light. Non-UV active
compounds were visualized by staining the developed glass plates with an aqueous solution of
molybdophosphorous acid or an aqueous solution of potassium permanganate (heating with a
hot gun). Staining solutions were prepared as follow: Ceric ammonium molybdate: 24 g
ammonium molybdate [(NH
4
)
6
Mo
7
O
24
•4H
2

O] and 0.5 g Ce(NH
4
)
2
(NO
3
)
6
were dissolved in
400 mL of aqueous 10% H
2
SO
4
. Potassium permanganate: 2.5 g KMnO
4
and 12.5 g
Na
2
CO
3
in 250 mL H
2
O.
Appendix 1
176

Flash chromatography and dry column vacuum chromatography (DCVC) were performed
using EMD or Silicycle
®
silica gel 40–63 µm particle size, 40 or 60 Å pore size and 25–40

µm particle size, 60 Å pore size, respectively.
Analytical HPLC-MS was performed using Shimadzu Prominence series connected with
ESI/TOF; column: XTerra
TM
MS C
18
, 2.5µm, 2.1·30mm; gradient: 0-0.5 min, 10% B; 0.5-3.5
min, 100% B; 3.5-9.0 min, 100% B; 9.0-9.5 min, 10% B; 9.5-15.0 min, 10% B; flow: 0.4
mL•min
-1
.
Preparative HPLC was performed using a Gilson machine (liquid handler GX-271, UV
detector UV/VIS 151 and pump model 321); column: XTerra
TM
prep MS C
18
OBD
TM
, 5µm,
19·50mm; gradient: optimized for each sample; flow: 10.0 mL•min
-1
.
X-ray crystallography
Crystals were mounted on glass fibres. X-ray data were collected with a Bruker AXS SMART
APEX diffractometer, using Mo-Kα radiation at 223K or at 100K, with the SMART suite of
programs (SMART, version 5.628, 2001. Bruker AXS Inc., Madison, Wisconsin, USA). Data
were processed and corrected for Lorentz and polarization effects with SAINT (SAINT+,
version 6.22a, 2001. Bruker AXS Inc., Madison, Wisconsin, USA), and for absorption effect
with SADABS (SADABS, version 2.10, 2001. G. W. Sheldrick, University of Goettingen,
Germany). Structural solution and refinement were carried out with the SHELXTL, suite of

programs (SHELXTL, version 6.14, 2000. Bruker AXS Inc., Madison, Wisconsin, USA). All
structures were solved by direct methods to locate the heavy atoms, followed by difference
maps for the light, non-hydrogen atoms. All non-hydrogen atoms were generally given
anisotropic displacement parameters in the final mode. All H-atoms were put at calculated
positions.
Experimental Section
177
Note: Copies of the coordinates for selected structures have been uploaded to the Cambridge
Crystallographic Data Centre (
Experimental procedures
All experimental procedures are arranged in the ascending order of numbers of the
compounds.
2,4-dihyroxy-5-iodoacetophenone (3-11)
1, 2
. Iodine monochloride (10.65 g,
65.6 mmol) in 30 mL of acetic acid was added over 30 min to a solution of
2,4-dihydroxyacetophenone (2-5) (9.5 g, 62.5 mmol) in 77 mL of glacial
acetic acid. After 4 h, the reaction was quenched by addition of a saturated
solution of sodium thiosulfate. The aqueous layer was extracted 4 times and the combined
organic layers were washed four times with water, dried over Na
2
SO
4
and evaporated under
vacuum. The residue was purified by silica gel column chromatography (hexane/EtOAc, 8/2)
to afford compound 3-11 (8.688 g, 50%) as a clear oil. IR (KBr): ν
max
= 3291, 2917, 2735,
1636, 1615, 1270 cm
-1

;
1
H NMR (300 MHz, CDCl
3
) δ 12.48 (s, 1 H), 8.02 (s, 1H), 6.59 (s, 1
H), 2.56 (s, 3H);
13
C NMR (75 MHz, CDCl
3
) δ 201.69, 165.21, 160.87, 140.76, 116.82,
103.56, 73.44, 26.25; EIMS
+
: m/z (%): 278 (80) [M]
+
, 263 (100), 136 (25), 108 (12), 41 (37);
HRMS (EI) m/z: 277.9440 [calcd. [M]
+
of 277.9440 for C
8
H
7
O
3
I].
2,4-bis(tosyloxy)-5-iodoacetophenone (3-2)
2
.

A mixture of 2,4-dihydroxy-
5-iodoacetophenone (3-11) (2.7 g, 9.71 mmol), p-toluenesulfonyl chloride

(5.7 g, 29.90 mmol) and anhydrous K
2
CO
3
(11.5 g, 83.21 mmol) in 150 mL
of anhydrous acetone was refluxed for 45 min. The reaction mixture was cooled, filtered
through Celite, washed with acetone and the filtrate was concentrated by rotary evaporation.
The residue was dissolved in water and extracted three times with 200 mL of DCM. The
3-11
OH
HO
O
I
OTs
TsO
O
I
3-2
Appendix 1
178

combined organic layers were washed with 70 mL of 1M HCl, water, and brine. The organic
layer was dried over Na
2
SO
4
and concentrated via rotary evaporation. The resulting crude
product was purified by flash column chromatography (5:1 hexane/EtOAc) to afford
compound 3-2 in 94% yield (5.3 g, 8.66 mmol) as white crystals. IR (KBr): ν
max

= 2960,
2927, 1695, 1596, 1585, 1466, 1355 cm
-1
;
1
H-NMR (500 MHz, CDCl
3
) δ 8.03 (s, 1H), 7.75
(dd, J = 1.4, 6.8 Hz, 2H), 7.71 (dd, J = 1.4, 7.0 Hz, 2H), 7.36 (d, J = 8.2 Hz, 2H), 7.34 (dd, J =
8.2 Hz, 2H), 7.12 (s, 1H), 2.52 (s, 3H), 2.48 (s, 3H), 2.47 (s, 3H);
13
C-NMR (125 MHz,
CDCl
3
) δ 195.31, 152.38, 147.83, 146.64, 146.40, 140.92, 132.86, 132.17, 131.36, 130.31,
130.05, 128.83, 128.56, 117.58, 88.12, 30.43, 21.80; EIMS
+
: m/z (%): 586 (10) [M]
+
, 417
(32), 154 (89), 138 (15), 91 (100); HRMS (EI) m/z: 585.9623 [calcd. [M]
+
of 585.9617 for
C
22
H
19
O
7
IS

2
].
((3-methylpenta-1,4-diyn-3-yloxy)methyl)benzene (3-3). A solution of 4-
trimethylsilyl-3-butynl-2-one (3-1) (1.4 g, 10.0 mmol) in 10 mL of anhydrous
THF was added to a 0.5 M solution of ethynylmagnesium bromide in THF (60 mL, 30.0
mmol) at 0 °C. After the addition, the reaction mixture was slowly warmed up to 23 °C and
then refluxed for 1 h. After cooling to 23 °C, the resulting brown solution was diluted with
100 mL of Et
2
O and treated slowly with 30 mL of saturated NH
4
Cl. The organic layer was
collected and the aqueous layer was washed twice with 100 mL of Et
2
O. The combined
organic layers were extracted sequentially with 30 mL of saturated NH
4
Cl, water and brine,
dried over Na
2
SO
4
and the solvent was removed on a rotary evaporator at < 23 °C (note: the
product is highly volatile). The resulting brown oil was dissolved in anhydrous DMF. NaH
(0.6 g. 15 mmol) was added to this solution in portions. After 15 min, n-Bu
4
NI (0.369 g, 1
mmol) and benzyl bromide (1.7 g, 10.0 mmol) were added sequentially. After 18 h, the
solvent was removed on a rotary evaporator at 40 °C. The crude product was dissolved in
water and extracted three times with 70 mL of Et

2
O. The combined organic layers were
OBn
3-3
Experimental Section
179
washed with 50 mL of 1M HCl, water and brine, dried over Na
2
SO
4
and concentrated via
rotary evaporation. The crude product was purified by flash chromatography (98:2
hexane/EtOAc) to afford intermediate 3-3 as a viscous colourless oil, which crystallised after
storage for 24 h at -20 °C giving white crystals in 27% yield (0.501 g, 2.72 mmol). IR (KBr):
ν
max
= 3281, 3246, 3007, 2861, 2116, 1378 cm
-1
;
1
H-NMR (500 MHz, CDCl
3
) δ 7.41-7.28
(m, 5H), 4.78 (s, 2H), 2.60 (s, 2H), 1.85 (s, 3H);
13
C-NMR (125 MHz, CDCl
3
) δ 137.82,
128.33, 128.09, 127.68, 82.42, 72.56, 68.37, 30.74; EIMS
+

: m/z (%): 153 (65), 141 (20), 91
(100), 77 (63); HRMS (EI) m/z: 183.0808 [calcd. [M–H]ˉ of 184.0888 for C
13
H
12
O].
For synthetic intermediate 3-3, a small colourless block, 0.8 x 0.64 x 0.16 mm, was used for
X-ray crystallographic data collection at 223(2) K using Mo (Kα) radiation. 7372 reflections
were collected and 2458 were unique (R
int
= 0.0271). No symmetry higher than monoclinic
was observed and the centrosymmetric alternative, P2
1
/c, was chosen based on the results of
refinement. Direct methods were used to solve the structure and all non-hydrogen atoms were
refined anisotropically. All H atoms were placed in idealized locations. For C
13
H
12
O,
monoclinic, P2
1
/c, a = 12.5415(10), b = 6.7365(5), c = 13.0122(11) Å, α = 90, β = 102.770(2),
γ = 90 °, V = 1072.15(15) Å
3
, Z = 4, Dx = 1.141 Mg/m
3
, R1 = 0.0468, wR2 = 0.1108 based on
2σ(I) data. A copy of the coordinates for structure 3-3 has been uploaded to the Cambridge
Crystallographic Data Centre (

1,1’-(5,5’-(3-(benzyloxy)-3-methylpenta-1,4-diyne-1,5-
diyl)-bis(2,4-tosyl-5,1-phenylene))-diethanone (3-24). A
solution of acetophenone 3-2 (10.98 g, 18.71 mmol),
acetylene derivative 3-3 (1.724 g, 9.36 mmol), PPh
3
(589
mg, 2.24 mmol), palladium dichloride (199.0 mg, 1.12 mmol), cuprous iodide (213.0 mg,
1.12 mmol) in a mixture of degassed DMF/triethylamine (23 mL/70 mL) was heated to 80˚C
for 4 h. After addition of 1M HCl, the mixture is extracted three times with 100 mL EtOAc.
Appendix 1
180

The combined organic layers were washed successively with 70 mL of 1M HCl, 70 mL of
water and brine, dried over Na
2
SO
4
and evaporated under vacuum. The residue was purified
by silica gel chromatography (hexane/EtOAc, 65/35 to hexane/EtOAc, 50/50) to afford
compound 3-24 (8.30 g, 81%) as a yellow wax. IR (NaCl): ν
max
= 3064, 2925, 1700, 1593,
1480, 1384, cm
-1
;
1
H-NMR (500 MHz, CDCl
3
) δ 7.77 (s, 2H), 7.71 (d, J = 8.3 Hz, 4H), 7.69
(d, J = 8.4 Hz, 4H), 7.34 (d, J = 8.3 Hz, 4H), 7.23 (d, J = 8.3 Hz, 4H), 7.14 (s, 2H), 4.77 (s,

2H), 2.50 (s, 6H), 2.47 (s, 6H), 2.36 (s, 6H), 1.85 (s, 3H);
13
C-NMR (75 MHz, CDCl
3
) δ
195.61, 151.85, 147.18, 146.56, 146.15, 137.66, 135.10, 134.64, 134.55, 134.46, 131.81,
131.24, 130.19, 129.97, 129.68, 128.45, 128.5, 128.25, 128.01, 127.62, 117.45, 116.02, 94.01,
77.63, 68.67, 66.55, 30.33, 30.28, 21.70, 21.57; ESIMS
+
: m/z (%): 1123 (100) [M+Na]
+
, 861
(17), 707 (31); HRMS (ESI) m/z: 1123.1775 [calcd. [M+Na]
+
of 1123.1768 for C
57
H
48
O
15
Na
S
4
].
1,1’-(5,5’-(3-(benzyloxy)-3-methylpenta-1,4-diyne-1,5-di-
yl)bis(2,4-hydroxy-5,1-phenylene))diethanone (3-4). For
reliability, we activated our magnesium turnings by stirring
over 1M HCl for 5 mins, filtering, washing with acetone and
Et
2

O, and drying under high vacuum for 2 hours. A solution of compound 3-24 (8.00 g, 7.26
mmol) and freshly activated magnesium turnings (7.06 g, 290.42 mmol) in 150 mL of MeOH
was stirred for 20 h. After addition of 300 mL of 10% citric acid, the mixture was extracted
three times with 200 mL of EtOAc. The combined organic layers were washed twice with 200
mL of water and 200 mL of brine, dried over Na
2
SO
4
and evaporated under vacuum. The
resulting crude product was purified by flash column chromatography (3:2 hexane/EtOAc) to
afford compound 3-4 in 61% yield (2.14 g, 4.41 mmol) as a clear oil. IR (NaCl): ν
max
= 2922,
1640, 1490, 1411, 1368, 1293 cm
-1
;
1
H-NMR (500 MHz, CDCl
3
) δ 12.74 (s, OH, 2H), 7.80
(s, 2H), 7.40 (d, J = 7.5 Hz, 2H), 7.35 (t, J = 7.4 Hz, 2H), 7.30 (d, J = 7.4 Hz, 1H), 6.50 (s,
Experimental Section
181
2H), 4.91 (s, 2H), 2.58 (s, 6H), 2.07 (s, 3H);
13
C-NMR (75 MHz, CDCl
3
) δ 202.6, 166.0,
163.0, 136.0, 128.7, 128.2, 128.0, 127.1, 114.8, 104.1, 103.6, 101.1, 94.1, 78.4, 68.9, 67.3,
31.5, 26.5; ESIMSˉ: m/z (%): 967 (74) [2M–H]ˉ,637 (12), 505 (28), 483 (100) [M–H]ˉ, 375

(14) [M–OBn]ˉ; HRMS (ESI) m/z: 483.1455 [calcd. [M–H]ˉ of 483.1449 for C
29
H
23
O
7
].
1,1'-(2,2'-(1-(benzyloxy)ethane-1,1-diyl)bis(6-hydroxyl-
benzofuran-5,2-diyl))diethanone (3-5). A solution of
dialkyne 3-4 (2.0 g, 4.13 mmol) , cuprous iodide (200.0 mg,
1.05 mmol) and triethylamine (4.2 g, 41.5 mmol) in 30 mL
of DMF was heated at 60˚C for 2 hours. The reaction mixture was poured into 100 mL of 1M
HCl and extracted three times with 30 mL of Et
2
O. The combined organic layers were washed
with 50 mL of 1M HCl, saturated NaHCO
3
, water and brine. The organic layer was dried over
Na
2
SO
4
and the solvent was removed on a rotary evaporator. The resulting crude product was
purified by flash column chromatography (3:1 hexane/EtOAc) to afford 3-5 in 75% yield
(1.51 g, 3.11 mmol) as a light yellow oil. IR (NaCl): ν
max
= 3435, 2927, 1645, 1448, 1371,
cm
-1
;

1
H-NMR (500 MHz, CDCl
3
) δ 12.45 (s, 2H), 7.97 (s, 2H), 7.34-7.27 (m, 5H), 7.01 (s,
2H), 6.80 (s, 1H), 6.80 (s, 1H), 4.52 (s, 2H), 2.69 (s, 6H), 2.11 (s, 3H);
13
C-NMR (75 MHz,
CDCl
3
) δ 203.96, 161.33, 159.58, 157.88, 128.56, 128.35, 127.62, 127.45, 126.97, 124.02,
120.63, 117.17, 105.18, 99.95, 99.67, 74.88, 66.66, 65.40, 26.83, 23.35; ESIMSˉ: m/z (%):
483 (28) [M–H]ˉ, 375 (100) [M–OBn]ˉ; HRMS (ESI) m/z: 483.1416 [calcd. [M–H]ˉ of
483.1438 for C
29
H
23
O
7
].
Iso-laetirobin A (3-26). A 1.0M solution of BCl
3
in hexane
(154 µL, 0.154 mmol) was added to 3-5 (50 mg, 0.103
mmol) in 5 mL of anhydrous DCM at -78 °C. The reaction
mixture was stirred at this temperature for 15 min. The
Appendix 1
182

reaction was terminated by the addition of 5 mL of water and slowly warmed to 23 °C over
1.5 h. The reaction mixture was extracted three times with 10 mL of DCM. The combined

organic layers were washed with 10 mL of 5% NaHCO
3
, water and brine. The organic layer
was dried over Na
2
SO
4
and the solvent was removed on a rotary evaporator. The resulting
crude product was purified by preparative HPLC on a Waters SunFire C
18
OBD 19x50 mm, 5
µm with a gradient: 10 to 100% CH
3
CN in 30 min to afford iso-laetirobin A (3-26) in 24%
yield, as a yellow-brown oil (9.5 mg, 0.013 mmol). IR (NaCl): ν
max
= 3434, 1638, 1452,
1355, 1241 cm
-1
;
1
H-NMR (500 MHz, CDCl
3
) δ 12.86 (s, 1H), 12.57 (s, 1H), 12.55 (s, 1H),
12.39 (s, 1H), 7.92 (s, 1H), 7.89 (s, 1H), 7.85 (s, 1H), 7.27 (s, 1H), 7.01 (s, 1H), 6.77 (s, 1H),
6.57 (s, 1H), 6.30 (s, 1H), 6.28 (s, 1H), 6.19 (s, 1H), 4.80 (s, 1H), 4.18 (d, J = 18.0 Hz, 1H),
3.68 (d, J = 18.0 Hz, 1H), 2.73 (s, 3H), 2.67 (s, 3H), 2.63 (s, 3H), 2.01 (d, J = 2.0 Hz, 3H)
1.63 (s, 3H);
13
C-NMR (125 MHz, CDCl

3
) δ 204.19, 204.13, 204.04, 202.66, 165.92, 163.83,
161.45, 158.59, 155.64, 153.47, 150.83, 127.83, 124.30, 123.70, 120.16, 116.86, 115.07,
110.14, 105.28, 105.20, 100.32, 99.97, 99.80, 98.82, 47.53, 27.20, 27.15, 27.05, 25.27, 11.69;
ESIMSˉ: m/z (%): 751 (100) [M–H]ˉ; HRMS (EI) m/z: 752.1892 [calcd. [M]
+
of 752.1894
for C
44
H
32
O
12
].
Crystals were obtained upon recrystallisation from a dichloromethane/methanol mixture. For
synthetic intermediate 3-26, a small block, 0.40 x 0.20 x 0.18 mm, was used for X-ray
crystallographic data collection at 223(2) K using Mo (Kα) radiation. 12405 reflections were
collected and 8291 were unique (R
int
= 0.0276). No symmetry higher than triclinic was
observed and the centrosymmetric alternative, Pī, was chosen based on the results of
refinement. Direct methods were used to solve the structure and all non-hydrogen atoms were
refined anisotropically. All H atoms were placed in idealized locations. For C
44
H
32
O
12
,
triclinic, Pī, a = 11.9232(17), b = 12.0133(16), c = 13.613(2) Å, α = 97.200(3), β =

109.150(3),
γ = 90.874(3) °, V = 1824.1(4) Å
3
, Z = 2, Dx = 1.400 Mg/m
3
, R1 = 0.0759, wR2 =
Experimental Section
183
0.2006 based on 2σ(I) data. A copy of the coordinates for structure 3-26 has been uploaded to
the Cambridge Crystallographic Data Centre (
Synthetic laetirobin A (2-1). Benzyloxy-protected bis-
benzo[b]furan 3-5 (797.0 mg, 1.645 mmol) was dissolved in
50 mL of a mixture of 5% MeOH in DCM. Subsequently,
0.5 mL of 1% aqueous 1.0 M HCl was added and the
mixture was stirred for 30 h at 23 °C and under ambient
atmosphere. The reaction mixture was poured into 30 mL
saturated sodium bicarbonate solution and extracted three times with 20 mL of DCM. The
combined organic layers were washed with 20 mL water and brine. The organic layer was
dried over Na
2
SO
4
and the solvent was removed on a rotary evaporator. The resulting crude
product was purified by preparative HPLC on a Waters SunFire C
18
OBD 19x50 mm, 5 µm
with a gradient: 10 to 100% CH
3
CN in 30 min to afford synthetic laetirobin A (2-1) in 64%
yield (399 mg, 0.530 mmol) as a light yellow solid. IR (KBr): ν

max
= 3516, 2925, 1644, 1465,
1369, 1254 cm
-1
;
1
H-NMR (500 MHz, CDCl
3
) δ 12.45 (s, OH, 2H), 12.44 (s, OH, 1H), 12.37
(s, OH, 1H), 7.92 (s, 1H), 7.91 (s, 1H), 7.90 (s, 1H), 7.68 (s, 1H), 7.00 (s, 1H), 6.96 (s, 1H),
6.96 (s, 2H), 6.57 (s, 1H), 6.48 (s, 1H), 6.47 (s, 1H), 6.47 (s, 1H), 4.47 (t, J = 5.5 Hz, 1H),
2.76 (m, 1H), 2.69 (m, 1H), 2.66 (s, 3H), 2.65 (s, 6H), 2.36 (m, 1H), 2.35 (s, 3H), 2.32 (m,
1H);
13
C-NMR (125 MHz, CDCl
3
) δ 204.2, 204.2, 204.1, 204.0, 161.5, 161.5, 161.4, 161.3,
159.8, 159.7, 159.7, 159.6, 158.7, 158.2, 157.3, 153.7, 144.7, 123.9, 123.9, 123.6, 123.3,
121.2, 120.8, 120.7, 119.5, 117.4, 117.2, 117.2, 115.9, 106.0, 105.6, 104.4, 100.4, 100.1,
100.1, 100.0, 43.5, 34.7, 31.3, 27.1, 27.1, 27.1, 26.9, 25.5; EIMSˉ: m/z (%): 751 (33) [M–H]ˉ;
HRMS (EI) m/z: 752.1882 [calcd. [M]
+
of 752.1894 for C
44
H
32
O
12
].
Crystals were obtained upon recrystallisation from a dichloromethane/methanol mixture. For

synthetic laetirobin A (
2-1), a small orange block, 0.16 x 0.10 x 0.08 mm, was used for X-ray
O
O
O
O
HO
O
HO
O
HO
O
OH
O
2-1
Appendix 1
184

O
O
O
O
O
O
HO
O
HO
O
OH
O

4-38
O
O
crystallographic data collection at 223(2) K using Mo (Kα) radiation. 14236 reflections were
collected and 9076 were unique (R
int
= 0.0342). No symmetry higher than triclinic was
observed and the centrosymmetric alternative, Pī, was chosen based on the results of
refinement. Direct methods were used to solve the structure and all non-hydrogen atoms were
refined anisotropically. All H atoms were placed in idealized locations. For C
44
H
32
O
12
,
triclinic, Pī, a = 10.9989(12), b = 13.8100(14), c = 14.2340(15) Å, α = 112.139(2), β =
90.723(3), γ = 94.576(3) °, V = 1994.1(4) Å
3
, Z = 2, Dx = 1.452 Mg/m
3
, R1 = 0.0709, wR2 =
0.1967 based on 2σ(I) data. A copy of the coordinates for structure 2-1 has been uploaded to
the Cambridge Crystallographic Data Centre (
Ethyl 2-(5-acetyl-2-((9bS)-8-acetyl-1,4-bis(5-acetyl-6-
hydroxybenzofuran-2-yl)-7-hydroxy-1,2,3,9b-tetra-
hydrodibenzo[b,d]furan-1-yl)benzofuran-6-yloxy)
acetate (4-38). Laetirobin A (2-1) (10.0 mg, 0.013
mmol) and dry K
2

CO
3
(19.0 mg, 0.014 mmol) were
dissolved in 2 mL of anhydrous DMF under an inert
atmosphere of argon. Subsequently, ethyl bromoacetate
(4-32) (2.3 mg, 0.014 mmol dissolved in 410 µl of
anhydrous DMF) was added via syringe pump (1 mL/h) to the reaction mixture. After being
stirred for 5 h at 23 °C, the reaction mixture was poured into 10 mL of water and extracted
three times with 5 mL of EtOAc. The combined organic layers were washed with 10 mL
water and brine. The organic layer was dried over Na
2
SO
4
and the solvent was removed on a
rotary evaporator. The resulting crude product was purified by flash column chromatography
(3:2 hexane/EtOAc) to obtain a compound 4-38 enriched crude product. Consecutive
preparative TLC purification steps (2:1 hexane/EtOAc, 2x developed followed by 3:2
hexane/EtOAc, 3x developed) was conducted to afford
4-38 in 27% yield (3.0 mg, 0.004
Experimental Section
185
O
O
O
O
O
O
HO
O
HO

O
OH
O
4-43
O
HN
NH
O
O
O
N
mmol) as a light yellow solid.
1
H-NMR (500 MHz, CDCl
3
) δ 12.45 (s, OH, 3H, major), 12.37
(s, OH, 3H, minor), 7.92 (s, 1H), 7.95-7.90 (m, 4H), 7.72-7,63 (m, 1H), 7.02-6.89 (m, 4H),
6.58-6.45 (m 4H), 4,72 (s, 3H), 4.51-4.48 (m, 1H), 4.30-4.26 (m, 3H), 2.74-2.62 (m, 17H),
2.38-2.33 (m, 4H), 1.33-1.29 (m, 4H) (Note: inseparable mixture of either diastreomers or two
differently mono-labelled compounds); HRMS (EI) m/z: 839.2318 [calcd. [M+H]
+
of
839.2340 for C
48
H
39
O
14
].
2-(5-acetyl-2-((9bS)-8-acetyl-1,4-bis(5-acetyl-6-hydroxy

benzofuran-2-yl)-7-hydroxy-1,2,3,9b-tetrahydrodi-
benzo[b,d]furan-1-yl)benzofuran-6-yloxy)-N-(2-(2-(7-
(dimethylamino)-2-oxo-2H-chromen-4-yl)acetamido)-
ethyl)acetamide (4-43). Ester 4-38 (3.0 mg, 0.004 mmol)
and LiOH (1.0 mg, 0.021 mmol) were dissolved in 9 mL
of a mixture of EtOH and water (2/1) under an inert
atmosphere of argon. The reaction mixture was stirred for 18 h at 23 °C and poured into 10
mL of water. The pH value of the mixture was adjusted to 1 using 1M HCl before extraction
with 5 mL of EtOAc (three times). The combined organic layers were washed with 10 mL
water and brine. The organic layer was dried over Na
2
SO
4
and the solvent was removed on a
rotary evaporator. The resulting crude acid 4-39 was dried on the high vacuum overnight.
Subsequently, amine 4-42·TFA (4.2 mg, 0.015 mmol), HATU (4.2 mg, 0.011 mmol) and
HOAt (1.6 mg, 0.011 mmol) were added to the crude acid which was dissolved in 1 mL of
DCM under an inert atmosphere of argon prior to the addition of reagents. After the addition
of triethylamine (200 µl), the reaction mixture was stirred for 18 h at 23 °C and poured into
10 mL of water. The pH value of the mixture was adjusted to 1 using 1M HCl before
extraction with 5 mL of DCM (three times). The combined organic layers were washed with
10 mL water and brine. The organic layer was dried over Na
2
SO
4
and the solvent was
Appendix 1
186

removed on a rotary evaporator. The resulting crude amide was purified by flash column

chromatography (2:3 hexane/EtOAc) to obtain a compound 4-43 enriched crude product.
Consecutive preparative TLC purification steps (2:1 hexane/EtOAc, 3x developed followed
by 99:1 DCM/MeOH, 3x developed) was conducted to afford 4-43 in 27% yield (3.0 mg,
0.004 mmol) as a light yellow solid. HRMS (EI) m/z: 1082.2229 [calcd. [M+H]
+
of
1082.3338 for C
61
H
52
O
16
N
3
] ) (Note: inseparable mixture of either diastreomers or two
differently mono-labelled compounds).
1,1-di(benzo[b]furan-2-yl)ethanol (5-2). A solution of benzo[b]-
furan 3-49 (100 mg, 0.85 mmol) in freshly distilled THF (3 mL) was
added to a solution of n-butyllithium (0.6 mL of a 1.6 M solution in
hexane, 0.94 mmol) in THF (3 mL) at -78 ºC. After being stirred at -78 ºC for 1 h, the solution
was transferred via cannula to a solution of 2-acetylbenzo[b]furan 5-1 (136.0mg, 0.85 mmol)
in THF (6 mL) cooled to -78 ºC. After being stirred for 2 h at -78 ºC, the reaction mixture was
poured into water. The aqueous layer was extracted three times with 15 mL of Et
2
O. The
combined organic layers were washed with 10 mL water and brine. The organic layer was
dried over Na
2
SO
4

and the solvent was removed on a rotary evaporator. The resulting crude
product was purified by preparative HPLC on a Waters SunFire C
18
OBD 19x50 mm, 5 µm
with a gradient: 10 to 100% CH
3
CN in 30 min to afford 5-2 in 41% yield (97 mg, 0.35 mmol)
as a white solid. IR (KBr): ν
max
= 3387, 3063, 1450, 1373, 1250 cm
-1
;
1
H-NMR (300 MHz,
CDCl
3
) δ 7.54 (d, J = 7.23 Hz, 2H), 7.44 (d, J = 7.89 Hz, 2H), 7.24 (m, 4H), 6.71 (s, 2H), 3.04
(bs, 1H), 2.09 (s, 3H);
13
C-NMR (75 MHz, CDCl
3
) δ 158.95, 154.86, 128.01, 124.46, 122.94,
121.26, 111.37, 103.07, 70.12, 25.94; ESIMSˉ: m/z (%): 277 (100) [M]ˉ, 159 (28), 113 (22);
HRMS (ESI) m/z: 277.0883 [calcd. [M–H]ˉ of 277.0870 for C
18
H
13
O
3
].

Experimental Section
187

1,1,4-tri(benzo[b]furan-2-yl)-1,2,3,9b-tetrahydroidbenzo[b,d]-
furan (5-4). To a solution of compound 5-2 (30.0 mg, 0.108
mmol) in freshly distilled THF (4 mL) was added Burgess
reagent (77.0 mg, 0.324 mmol). The reaction mixture was stirred
under an inert atmosphere of argon for 20 h. The reaction was poured into 20 mL of water and
extracted three times with 10 mL of Et
2
O. The combined organic layers were washed with 10
mL of water and brine. The organic layer was dried over Na
2
SO
4
and the solvent was
removed on a rotary evaporator. The resulting crude product was purified by preparative
HPLC on a Waters SunFire C
18
OBD 19x50 mm, 5 µm with a gradient: 10 to 100% CH
3
CN
in 30 min to afford 5-4 in 89% yield (25 mg, 0.048 mmol) as a white solid. IR (NaCl) ν
max
=
3064, 2892, 1691, 1594, 1457, 1241 cm
-1
;
1

H-NMR (300 MHz, CDCl
3
) δ 7.52 (m, 3H), 7.39
(m, 2H), 7.31 (m, 3H), 7.19 (m, 4H), 7.11 (m, 1H), 7.05 (s, 1H), 6.87 (t, J = 7.40 Hz, 1H),
6.70 (d, J = 7.38 Hz, 1H), 6.36 (s, 1H), 5.97 (s, 1H), 5.26 (s, 1H), 2.87 (m, 4H);
13
C-NMR
(125 MHz, CDCl
3
) δ 159.42, 158.10, 155.06, 155.03, 154.19, 153.80, 153.25, 151.98, 129.50,
129.03, 128.39, 128.12, 124.42, 123.22, 122.83, 121.34, 121.29, 120.66, 111.49, 111.23,
111.01, 110.55, 106.10, 104.92, 103.99, 99.99, 49.34, 45.07, 33.33, 22.61; ESIMS
+
: m/z (%):
559 (15) [M+K]
+
, 543 (60) [M+Na]
+
, 521 (100) [M+H]
+
, 419 (11), 261 (13) [M/2+H]
+
;
HRMS (ESI) m/z: 543.1569 [calcd. [M+Na]
+
of 543.1567 for C
36
H
24
O

4
Na].
Crystals were obtained upon recrystallisation from a dichloromethane/methanol mixture. For
the [4+2]-cycloadduct 5-4, a small colourless block, 0.48 x 0.12 x 0.08 mm, was used for X-
ray crystallographic data collection at 223(2) K using Mo (Kα) radiation. 18023 reflections
were collected and 5865 were unique (R
int
= 0.0421). No symmetry higher than monoclinic
was observed and the centrosymmetric alternative, P2
1
/c, was chosen based on the results of
refinement. Direct methods were used to solve the structure and all non-hydrogen atoms were
O
O
O
O
H
5-4
Appendix 1
188

refined anisotropically. All H atoms were placed in idealized locations. For C
36
H
24
O
4
,
monoclinic, P2
1

/c, a = 10.0478(6), b = 28.418(2), c = 9.3323(6) Å, α = 90, β = 105.343(2), γ =
90 °, V = 2569.7(3) Å
3
, Z = 4, Dx = 1.346 Mg/m
3
, R1 = 0.0626, wR2 = 0.1441 based on 2σ(I)
data. A copy of the coordinates for structure 5-4 has been uploaded to the Cambridge
Crystallographic Data Centre (
[5+2]-cycloadduct (5-6). A 1.0M solution of BCl
3
in hexane (320
µL, 0.320 mmol) was added to 5-2 (60 mg, 0.216 mmol) in 5 mL of
anhydrous DCM at -78 °C. The deep purple reaction mixture was
stirred at this temperature for 15 min. The reaction was terminated by
the addition of 10 mL of water and slowly warmed to 23 °C over 1.5 h. The reaction mixture
was extracted three times with 10 mL of DCM. The combined organic layers were washed
with 10 mL of 5% NaHCO
3
, water and brine. The organic layer was dried over Na
2
SO
4
and
the solvent was removed on a rotary evaporator. After silica gel chromatography 18.0 mg of a
yellow powder (32%, 0.035 mmol) of the [5+2] cycloadduct 5-6 was isolated. For
unambiguous structure determination, 13.0 mg of this material was further purified by
preparative HPLC on a Waters SunFire C
18
OBD 19x50 mm, 5 µm column with a gradient:
10 to 100% CH

3
CN in 30 min to afford 4.7 mg of 5-6 as a light yellow solid. IR (NaCl) ν
max

= 2897, 1638, 1442, 1420, 1253 cm
-1
;
1
H-NMR (300 MHz, CDCl
3
) δ 7.64 (m, 1H), 7.53 (m,
1H), 7.46 (m, 2H), 7.38 (m, 2H), 7.29 (s, 2H), 7.17 (m, 5H), 7.01 (d, J = 8.07 Hz, 1H), 6.66 (t,
J = 7.56 Hz, 1H), 6.27 (s, 1H), 6.15 (s, 1H), 5.98 (d, J = 7.74 Hz, 1H), 5.01 (s, 1H), 4.25 (d, J
= 18 Hz, 1H), 3.76 (dd, J = 1.6 Hz, 18 Hz, 1H), 2.06 (d, J = 2 Hz, 3H) ;
13
C-NMR (125 MHz,
CDCl
3
) δ 158.97, 157.98, 155.88, 154.77, 154.56, 153.86, 153.55, 150.66, 130.96, 128.29,
127.16, 125.54, 122.82, 122.68, 122.03, 121.57, 121.11, 118.32, 111.66, 111.39, 110.90,
110.14, 109.55, 106.74, 104.95, 103.72, 52.64, 47.66, 34.66, 29.93, 11.77, 11.76; ESIMS
+
:
O
O
O
O
H
5-6
Experimental Section

189
m/z (%): 591 (57), 575 (100), 570 (24), 535 (31), 519 (71) [M–H]
+
, 419 (27), 247 (20);
HRMS (ESI) m/z: 519.1593 [calcd. [M–H]
+
of 519.1591 for C
36
H
23
O
4
].
Crystals were obtained upon recrystallisation from a dichloromethane/methanol mixture. For
the [5+2]-cycloadduct 5-6, a small colourless block, 0.32 x 0.18 x 0.08 mm, was used for X-
ray crystallographic data collection at 223(2) K using Mo (Kα) radiation. 16383 reflections
were collected and 5751 were unique (R
int
= 0.0241). No symmetry higher than triclinic was
observed and the centrosymmetric alternative, Pī, was chosen based on the results of
refinement. Direct methods were used to solve the structure and all non-hydrogen atoms were
refined anisotropically. All H atoms were placed in idealized locations. For C
36
H
24
O
4
,
triclinic, Pī, a = 9.6753(4), b = 11.4318(5), c = 12.7153(5) Å, α = 72.7480(10), β =
79.5670(10), γ = 69.6640(10) °, V = 1254.61(9) Å3, Z = 2, Dx = 1.378 Mg/m

3
, R1 = 0.0454,
wR2 = 0.1130 based on 2σ(I) data. A copy of the coordinates for structure 5-6 has been
uploaded to the Cambridge Crystallographic Data Centre (
1-(4-hydroxy-3-iodophenyl)ethanone (5-8)
3, 4
. 4-Hydroxyacetophenone (5-7)
(2.72 g, 20.0 mmol) was dissolved in 20 mL of THF/H
2
O (50/50, v/v). Iodine
(5.6 g, 22.0 mmol) and NaHCO
3
(1.84 g, 22.0 mmol) were crushed and mixed
together and added to the solution. After the mixture was stirred for 18 h at
room temperature, residual iodine was quenched by addition of a 5% aqueous solution of
sodium thiosulfate. The aqueous layer was extracted three times with Et
2
O (50 mL each) and
the combined organic layers were washed with saturated sodium thiosulfate solution (30 mL),
water (30 mL), brine (50 mL), dried over Na
2
SO
4
and evaporated under vacuum. The residue
was purified by silica gel column chromatography (DCM/MeOH, 95/5) to afford compound
5-8 in 19% yield (1.010 g, 3.82 mmol) as a clear oil. IR (NaCl): ν
max
= 3124, 2916, 1651,
1589, 1411, 1357, 1288 cm
-1

;
1
H NMR (500 MHz, CDCl
3
) δ 8.31 (d, J = 2.5 Hz, 1 H), 7.87
5-8
OH
O
I
Appendix 1
190

(dd, J = 2.5 Hz, 8.8 Hz, 1H), 7.03 (d, J = 8.8 Hz, 1 H), 5.86 (bs, 1H), 2.55 (s, 3H);
13
C NMR
(125 MHz, CDCl
3
) δ 195.36, 158.84, 139.30, 132.05, 130.98, 114.76, 85.83, 26.25; ESIMS
+
:
m/z (%): 421 (12), 316 (46), 288 (100), 173 (50); HRMS (ESI) m/z: 262.9578 [calcd. [M+H]
+

of 262.9569 for C
8
H
8
O
2
I].

4-acetyl-2-iodophenyl-4-methylbenzenesulfonate (5-9).

A mixture of 1-(4-
hydroxy-3-iodophenyl)ethanone (5-8) (1.00 g, 3.82 mmol), p-toluenesulfonyl
chloride (2.1 g, 11.0 mmol) and anhydrous K
2
CO
3
(4.2 g, 30.39 mmol) in 50
mL of anhydrous acetone was refluxed for 3 h. The reaction mixture was
cooled, filtered through Celite, washed with acetone and the filtrate was concentrated by
rotary evaporation. The residue was dissolved in water and extracted three times with 20 mL
of Et
2
O. The combined organic layers were washed with 20 mL of 1M HCl, water, and brine.
The organic layer was dried over Na
2
SO
4
and concentrated via rotary evaporation. The
resulting crude product was purified by flash column chromatography (hexane to
hexane/EtOAc, 4/1) to afford compound 5-9 in 80% yield (1.30 g, 3.05 mmol) as colourless
oil that solidified upon drying in high vacuum. IR (NaCl): ν
max
= 3062, 2924, 1689, 1589,
1473, 1381, 1242, 1180, 1095, 1033 cm
-1
;
1
H-NMR (500 MHz, CDCl

3
) δ 8.32 (d, J = 2.55
Hz, 1H), 7.91 (dd, J = 2.55, 8.8 Hz, 1H), 7.81 (d, J = 8.2 Hz, 2H), 7.44 (d, J = 8.8 Hz, 1H),
7.35 (d, J = 8.2 Hz, 2H), 2.57 (s, 3H), 2.46 (s, 3H);
13
C-NMR (125 MHz, CDCl
3
) δ 195.35,
153.28, 146.14, 140.22, 136.54, 132.54, 129.95, 129.62, 128.81, 122.68, 90.48, 26.54, 21.78;
EIMSˉ: m/z (%): 414 (100), 386 (46), 260 (52), 224 (21), 170 (42); HRMS (ESI) m/z:
416.9667 [calcd. [M+H]
+
of 416.9657 for C
15
H
13
O
4
IS].
2,2'-(3-(benzyloxy)-3-methylpenta-1,4-diyne-1,5-diyl)bis(4-
acetyl-2,1-phenylene)bis(4-methyl-enzenesulfonate) (5-10).
A solution of 4-acetyl-2-iodophenyl-4-methylbenzenesulfonate
OTs
O
I
5-9
Experimental Section
(5-9) (1.25 g, 3.0
mmol), bis
mmol), palladium dichloride (32.0

in a mixture of degassed DMF/triethylamine (5
After addition of 1M
HCl (
EtOAc
. The combined organic layers were washed successively with
(50 mL) and brine (50
mL
vacuum. The residue was
hexane/EtOAc
, 50/50) to afford
compound 5-14
were stored in the dark for several days which lead to colourless crystals of
compound 5-14 (13 mg,
6
1597, 1489, 1381, 1265, 1180, 1095, 1026 cm
1.9, 2H), 7.92 (dd, J
= 1.9, 8.2 Hz, 2H), 7.78 (m, 4H), 7.44 (m, 2H), 7.37 (m, 4H), 7.29 (m,
1H), 7.2
4 (m, 4H), 4.84 (s, 2H), 2.59 (s, 6H), 2.34 (s, 6H), 1.91 (s, 3H);
CDCl
3
) δ
195.94, 153.01, 145.87, 137.94, 135.35, 134.26, 132.29, 129.89, 129.77, 128.54,
128.29, 128.14, 127.62, 122.48, 117.44, 93.57, 78.56, 68.72, 66.74, 30.48, 26.58, 21.60;
ESIMS
+
: m/z
(%): 806 (24), 783 (55), 778 (100);
[M+Na]
+

For (5-
14
(m, 12H), 7.31 (m, 6H), 7.20 (m, 13H), 7.16 (s, 1H), 7.14 (m, 1H), 6.89
(dd, J
= 8.2, 2.5 Hz, 1H), 6.39 (d,
3H);
13
C NMR
153.14,
153.11, 144.91, 139.17, 139.12
133.39, 131.98, 131.79, 131.60, 129.93, 129.74, 128.27, 127.99, 127.86, 127.83, 127.78,
124.31, 116.41, 26.02, 21.69;
mmol), bis
-acetylene 3-3 (0.276 g, 1.5
mmol), PPh
mmol), palladium dichloride (32.0
mg, 0.180 mmol), cuprous iodide
(34.3
in a mixture of degassed DMF/triethylamine (5
mL/15 mL
) was heated to 80
HCl (
100 mL
), the mixture was extracted three times with 50
. The combined organic layers were washed successively with
1M
mL
).The organic layer was dried over Na
2
SO

4

vacuum. The residue was
purified by silica gel chromatography (hexane/
, 50/50) to afford
5-10 (0.87 g, 76%) as a clear oil
. Fractions containing
were stored in the dark for several days which lead to colourless crystals of
6
%). For 5-10 IR (NaCl): ν
max

= 3062, 3001, 2931,
1597, 1489, 1381, 1265, 1180, 1095, 1026 cm
-1
;
1
H-NMR
(500 MHz, CDCl
= 1.9, 8.2 Hz, 2H), 7.78 (m, 4H), 7.44 (m, 2H), 7.37 (m, 4H), 7.29 (m,
4 (m, 4H), 4.84 (s, 2H), 2.59 (s, 6H), 2.34 (s, 6H), 1.91 (s, 3H);
195.94, 153.01, 145.87, 137.94, 135.35, 134.26, 132.29, 129.89, 129.77, 128.54,
128.29, 128.14, 127.62, 122.48, 117.44, 93.57, 78.56, 68.72, 66.74, 30.48, 26.58, 21.60;
(%): 806 (24), 783 (55), 778 (100);
HRMS (ESI)
m/z
+
of 783.1698 for C
43
H

36
O
9
NaS
2
].
14
)
1
H NMR (500 MHz, CDCl
3
) δ
7.61 (s, 1H), 7.60 (s, 1H), 7.51
(m, 12H), 7.31 (m, 6H), 7.20 (m, 13H), 7.16 (s, 1H), 7.14 (m, 1H), 6.89
= 8.2, 2.5 Hz, 1H), 6.39 (d,
J
= 8.2 Hz, 1H), 2.43 (s, 3H), 2.11 (s,
C NMR
(125 MHz, CDCl
3
) δ
196.98, 155.32, 153.44, 153.18,
153.11, 144.91, 139.17, 139.12
, 139.10, 135.01, 134.96, 134.92, 134.66, 134.30,
133.39, 131.98, 131.79, 131.60, 129.93, 129.74, 128.27, 127.99, 127.86, 127.83, 127.78,
124.31, 116.41, 26.02, 21.69;
31
P NMR (203 MHz, CDCl
3
) δ 23.39.

191
mmol), PPh
3
(94.4 mg, 0.360
(34.3
mg, 0.180 mmol)
) was heated to 80
°C for 4 h.
), the mixture was extracted three times with 50
mL
1M
HCl (50 mL), water

and evaporated under
purified by silica gel chromatography (hexane/
EtOAc, 65/35 to
. Fractions containing
were stored in the dark for several days which lead to colourless crystals of
= 3062, 3001, 2931,
2870, 1689,
(500 MHz, CDCl
3
) δ 8.09 (d, J =
= 1.9, 8.2 Hz, 2H), 7.78 (m, 4H), 7.44 (m, 2H), 7.37 (m, 4H), 7.29 (m,
4 (m, 4H), 4.84 (s, 2H), 2.59 (s, 6H), 2.34 (s, 6H), 1.91 (s, 3H);
13
C-NMR (125 MHz,
195.94, 153.01, 145.87, 137.94, 135.35, 134.26, 132.29, 129.89, 129.77, 128.54,
128.29, 128.14, 127.62, 122.48, 117.44, 93.57, 78.56, 68.72, 66.74, 30.48, 26.58, 21.60;
m/z

: 783.1731 [calcd.
7.61 (s, 1H), 7.60 (s, 1H), 7.51
(m, 12H), 7.31 (m, 6H), 7.20 (m, 13H), 7.16 (s, 1H), 7.14 (m, 1H), 6.89
= 8.2 Hz, 1H), 2.43 (s, 3H), 2.11 (s,
196.98, 155.32, 153.44, 153.18,
, 139.10, 135.01, 134.96, 134.92, 134.66, 134.30,
133.39, 131.98, 131.79, 131.60, 129.93, 129.74, 128.27, 127.99, 127.86, 127.83, 127.78,
Appendix 1
192

OBn
OH
O
OH
O
5-11
Crystals were obtained upon recrystallisation from a hexane/ethylacetate mixture. For the side
product 5-14, a small colourless block, 0.28 x 0.12 x 0.10 mm, was used for X-ray
crystallographic data collection at 100(2) K using Mo (Kα) radiation. 30598 reflections were
collected and 10023 were unique (R
int
= 0.0409). No symmetry higher than monoclinic was
observed and the centrosymmetric alternative, P2
1
/n, was chosen based on the results of
refinement. Direct methods were used to solve the structure and all non-hydrogen atoms were
refined anisotropically. All H atoms were placed in idealized locations. For C
51
H
43

IO
4
P
2
PdS,
monoclinic, P2
1
/n, a = 17.2514(6), b = 11.3058(4), c = 23.7741(9) Å, α = 90, β =
108.9530(10), γ = 90 °, V = 4385.5 Å
3
, Z = 4, Dx = 1.586 Mg/m
3
, R1 = 0.0507, wR2 =
0.1127 based on 2σ(I) data.
1,1'-(3,3'-(3-(benzyloxy)-3-methylpenta-1,4-diyne-1,5-diyl)-
bis-(4-hydroxy-3,1-phenylene))diethanone (5-11). For re-
liability, magnesium turnings were activated by stirring them
over 1M HCl for 5 minutes, filtering, washing with acetone and
Et
2
O, and drying under high vacuum for 2 hours. A solution of compound 5-10 (0.796 g, 1.05
mmol) and freshly activated magnesium turnings (0.510 g, 20.98 mmol) in 50 mL of MeOH
was stirred for 18 h. After addition of 50 mL of 10% citric acid, the mixture was extracted
three times with 30 mL of EtOAc. The combined organic layers were washed twice with 20
mL of 10% citric acid, 20 mL of water and 20 mL of brine, dried over Na
2
SO
4
and evaporated
under vacuum. The resulting crude product was purified by flash column chromatography

(3/1 hexane/EtOAc to 3/2 hexane/EtOAc) to afford compound 5-11 in 51% yield (0.253 g,
0.56 mmol) as a clear oil. IR (NaCl) ν
max
= 2922, 1640, 1490, 1411, 1368, 1293 cm
-1
;
1
H-
NMR (500 MHz, CDCl
3
) δ 8.03 (d, J = 1.9 Hz, 2H), 7.92 (dd, J = 1.9, 8.85 Hz, 2H), 7.36 (m,
5H), 7.00 (d, J = 8.85 Hz, 2H), 4.92 (s, 2H), 2.56 (s, 6H), 2.08 (s, 3H);
13
C-NMR (125 MHz,
CDCl
3
) δ 195.92, 160.77, 137.51, 133.38, 131.65, 130.29, 128.54, 128.49, 128.42, 128.00,
Experimental Section
193
127.85, 115.30, 108.53, 95.25, 78.51, 68.87, 67.08, 31.17, 26.32; ESIMSˉ: m/z (%): 903
(100) 565 (57), 451 (61); HRMS (ESI) m/z: 453.1712 [calcd. [M+H]
+
of 453.1702 for
C
29
H
25
O
5
].

1,1'-(2,2'-(1-(benzyloxy)ethane-1,1-diyl)bis(benzofuran-5,2-
diyl))diethanone (5-12). A solution of dialkyne 5-11 (170.0
mg, 0.38 mmol), cuprous iodide (18.0 mg, 0.095 mmol) and
triethylamine (425.0 mg, 4.20 mmol) in 5 mL of DMF was
heated at 60˚C for 2 hours. The reaction mixture was poured into 10 mL saturated aqueous
NH
4
Cl solution and extracted three times with 10 mL of Et
2
O. The combined organic layers
were washed with 10 mL of 1M HCl, saturated NaHCO
3
, water and brine. The organic layer
was dried over Na
2
SO
4
and the solvent was removed on a rotary evaporator. The resulting
crude product was purified by flash column chromatography (hexane to 3/1 hexane/EtOAc) to
afford 5-12 in 49% yield (83 mg, 0.18 mmol) as a colourless oil. IR (NaCl): ν
max
= 2916,
2854, 1681, 1589, 1435, 1357, 1265, 1118, 1056, 1026 cm
-1
;
1
H-NMR (500 MHz, CDCl
3
) δ

8.23 (d, J = 1.9 Hz, 2H), 7.96 (dd, J = 1.9, 8.85 Hz, 2H), 7.51 (d, J = 8.85 Hz, 2H), 7.32 (m,
5H), 6.95 (s, 2H), 4.54 (s, 2H), 2.66 (s, 6H), 2.17 (s, 3H);
13
C-NMR (125 MHz, CDCl
3
) δ
197.48, 158.72, 157.50, 137.97, 133.00, 128.36, 128.03, 127.63, 127.43, 125.35, 122.62,
111.53, 105.82, 75.11, 66.72, 26.76, 23.48; ESIMS
+
: m/z (%): 927 (72) [2M+Na]
+
, 344 (66)
[M–OBn]
+
, 167 (100); HRMS (ESI) m/z: 453.1682 [calcd. [M+H]
+
of 453.1702 for
C
29
H
25
O
5
].
1,1',1''-(2,2',2''-(8-acetyl-1,2,3,9b-tetrahydrodibenzo[b,d]-
furan-1,1,4-triyl)tris(benzofuran-5,2-diyl))triethanone (5-13)
Benzyloxy-protected bis-benzo[b]furan
5-12 (67.0 mg, 0.1481
O
O

O
O
O
O
O
O
5-13
Appendix 1
194

mmol) was dissolved in 10 mL of a mixture of 5% MeOH in DCM. Subsequently, 0.1 mL of
1% aqueous 1M HCl was added and the mixture was stirred for 5 days at 23 °C under ambient
atmosphere. The reaction mixture was poured into 10 mL saturated aqueous sodium
bicarbonate solution and extracted three times with 10 mL of DCM. The combined organic
layers were washed with 10 mL water and brine. The organic layer was dried over Na
2
SO
4

and the solvent was removed on a rotary evaporator. The resulting crude product was first
purified by preparative HPLC on a Waters SunFire C
18
OBD 19x50 mm, 5 µm with a
gradient: 10 to 100% CH
3
CN in 30 min, followed by preparative thin layer chromatography
and a final preparative HPLC on a Waters SunFire C
18
OBD 19x50 mm, 5 µm with a
gradient: 10 to 100% CH

3
CN in 30 min to afford compound 5-13 in 7% yield (3.5 mg, 0.005
mmol) as a colourless oil. IR (KBr): ν
max
= 3055, 2916, 2849, 1674, 1585, 1439, 1362, 1300,
1267, 1155, 810, 739 cm
-1
;
1
H-NMR (500 MHz, CDCl
3
) δ 8.18 (m, 3H), 7.95 (m, 5H), 7.51
(m, 4H), 6.71 (s, 1H), 6.65 (s, 1H), 6.64 (s, 1H), 4.63 (t, J = 5.7 Hz, 1H), 2.92 (m, 1H), 2.83
(m, 1H), 2.65 (s, 3H), 2.64 (s, 6H), 2.41 (s, 3H);

EIMSˉ: m/z (%): 687 (100) [M–H]ˉ; HRMS
(ESI) m/z: 689.2149 [calcd. [M+H]
+
of 689.2175 for C
44
H
33
O
8
].
4-iodobenzene-1,3-diol (5-16)
5
. Iodine monochloride (2.2 g, 13.58 mmol) in
13 mL of Et
2

O was added over 30 min to a stirring solution of resorcinol (5-
15) (1.36 g, 12.35 mmol) in 14 mL of Et
2
O. After 1 h, the reaction was
quenched by addition of a saturated solution of sodium thiosulfate. The aqueous layer was
extracted with 3 x 30 mL Et
2
O. The combined organic layers were washed 3 times with a
saturated solution of sodium thiosulfate, water, and brine, dried over Na
2
SO
4
and evaporated
under vacuum. The residue was purified by silica gel column chromatography (9/1
CHCl
3
/acetic acid) to afford compound 5-16 as a colourless oil in 25% yield. (0.730 g, 3.09
mmol).
1
H NMR (500 MHz, CDCl
3
) δ 7.45 (d, J = 8.8 Hz, 1 H), 6.54 (d, J = 3.15 Hz, 1 H),
Experimental Section
195
6.27 (dd, J = 3.15, 8.8 Hz, 1H), 5.15 (bs, 1H);
13
C NMR (125 MHz, CDCl
3
) δ 157.68, 155.70,
138.31, 110.43, 102.65, 74.49.

4-iodo-1,3-phenylene bis(4-methylbenzenesulfonate) (5-18).

A mixture of
4-iodobenzene-1,3-diol (5-16) (0.730 g, 3.09 mmol), p-toluenesulfonyl
chloride (1.77 g, 9.28 mmol) and anhydrous K
2
CO
3
(3.42 g, 24.74 mmol) in
40 mL of anhydrous acetone was refluxed for 1.5 hours. The reaction mixture was cooled,
filtered through Celite, washed with acetone and the filtrate was concentrated by rotary
evaporation. The residue was dissolved in water and extracted three times with 20 mL of
Et
2
O. The combined organic layers were washed with 30 mL of 1M HCl, water, and brine.
The organic layer was dried over Na
2
SO
4
and concentrated via rotary evaporation. The
resulting crude product was purified by flash column chromatography (from 100% hexane to
8/2 hexane/EtOAc) to afford compound 5-18 in 89% yield (1.42 g, 2.61 mmol) as a white
solid. IR (NaCl): ν
max
= 3062, 2924, 1597, 1465, 1381, 1188, 1111, 1026, 964 cm
-1
;
1
H-NMR

(500 MHz, CDCl
3
) δ 7.73 (dd, J = 8.2, 8.2 Hz, 4H), 7.67 (d, J = 8.2 Hz, 1H), 7.34 (dd, J =
8.2, 8.2 Hz, 4H), 6.97 (d, J = 2.5 Hz, 1H), 6.74 (dd, J = 2.5, 8.2 Hz, 1H), 2.46 (s, 6H);
13
C-
NMR (125 MHz, CDCl
3
) δ 150.30, 149.98, 146.08, 146.03, 140.11, 132.41, 131.74, 130.06,
129.92, 128.83, 128.49, 122.48, 117.50, 88.18, 21.78, 21.75; EIMS
+
: m/z (%): 561 (100)
[M+NH
4
]
+
; HRMS (ESI) m/z 566.9488 [calcd [M+Na]
+
of 566.9409 for C
20
H
17
O
6
INaS
2
].
Compound 5-19. A solution of protected dihydroxy-
benzene 5-18 (1.4 g, 2.57 mmol), acetylene derivative 3-3
(0.240 g, 1.30 mmol), PPh

3
(82.2 mg, 0.313 mmol),
palladium dichloride (28.0 mg, 0.158 mmol), cuprous iodide (30.0 mg, 0.158 mmol) in a
mixture of degassed DMF/triethylamine (5 mL/15 mL) was heated to 80 ˚C for 4 h. After
OTs
I
5-18
TsO
Appendix 1
196

addition of 1M HCl, the mixture is extracted three times with 80 mL EtOAc. The combined
organic layers were washed successively with 50 mL of 1M HCl, 50 mL of water and brine,
dried over Na
2
SO
4
and evaporated under vacuum. The residue was purified by silica gel
chromatography (hexane/EtOAc, 65/35 to hexane/EtOAc, 50/50) to afford compound 5-19 in
51% yield (0.680 g, 0.669 mmol) as a yellow wax. IR (NaCl): ν
max
= 3062, 2924, 1597, 1489,
1381, 1188, 1087, 964 cm
-1
;
1
H-NMR (500 MHz, CDCl
3
) δ 7.70 (m, 8H), 7.34 (m, 11H),
7.23 (m, 4H), 6.97 (d, J = 1.9 Hz, 2H), 6.91 (dd, J = 1.9, 8.2 Hz, 2H), 4.77 (s, 2H), 2.45 (s,

6H), 2.36 (s, 6H), 1.86 (s, 3H);
13
C-NMR (125 MHz, CDCl
3
) δ 150.17, 149.62, 146.03,
145.85, 137.97, 134.32, 132.14, 131.78, 130.04, 129.89, 128.60, 128.48, 128.32, 128.11,
127.63, 120.99, 117.16, 116.12, 93.59, 78.28, 68.65, 66.74, 30.50, 21.75, 21.66; ESIMS
+
: m/z
(%): 1039 (36) [M+Na]
+
, 1034 (100) [M+NH
4
]
+
, 500 (63), 352 (38); HRMS (ESI) m/z
1034.2034 [calcd [M+NH
4
]
+
of 1034.2008 for C
53
H
48
O
13
NS
4
].
Bis(6-methoxybenzo[b]furan-2-yl)methanone (3-40). A

neat mixture of 2-hydroxy-4-methoxy-benzaldehyde (3-
39) (300 mg, 1.97 mmol) and 1,3-dichloroacetone (3-30)
(125 mg, 0.98 mmol) was heated at 60˚C. At approximately 45 °C, the solid starting materials
started to melt. After 1 hour, freshly dried and grinded potassium phosphate (879 mg, 4.14
mmol) was added to reaction mixture and the mixture was heated to 80 °C for further 3 hours.
The brown powder formed was subsequently transferred into an Erlenmeyer flask containing
DCM (30 mL) and water (50 mL). The obtained suspension was stirred for 30 minutes and
transferred into a separating funnel. The aqueous phase was extracted two more times with 30
mL of DCM. The combined organic layers were washed twice with 30 mL of water and brine.
The organic layer was dried over Na
2
SO
4
and the solvent was removed on a rotary evaporator.
The resulting crude product was purified by flash column chromatography (4:1 hexane/EtOAc
to 1:1 hexane/EtOAc) to afford
3-40 in 36% yield (115 mg, 0.36 mmol) as a yellow solid. IR
Experimental Section
197
(NaCl): ν
max
= 2914, 1610, 1489, 1273, 1225, 1153, 1115, 1022, 928, 813, 735 cm
-1
;
1
H-
NMR (500 MHz, CDCl
3
) δ 7.92 (s, 2H), 7.61 (d, J = 8.8 Hz, 2H), 7.11 (d, J = 1.9, 2H), 6.97
(dd, J = 1.9, 8.8 Hz, 2H), 3.90 (s, 6H);

13
C-NMR (125 MHz, CDCl
3
) δ 170.50, 161.31,
157.40, 151.46, 123.68, 120.51, 116.24, 114.54, 95.57, 55.73; ESIMS
+
: m/z (%): 667 (100)
[2M+Na]
+
, 368 (32), 323 [M+H]
+
(40); HRMS (ESI) m/z: 323.0911 [calcd [M+H]
+
of
323.0919 for C
19
H
15
O
5
].
7-methoxy-1,1,4-tris(6-methoxybenzofuran-2-yl)-1,2,3,9b-
tetrahydrodibenzo[b,d]furan (5-22). To a solution of ketone
3-40 (20.0 mg, 0.06 mmol) in 2 mL of freshly distilled THF
was added methyl magnesiumbromide (11 mg, 0.09 mmol,
3.0M in Et
2
O) at 0 °C. After 0.5 hours, the ice bath was
removed and the mixture was stirred for 3.5 h at 23 °C under an inert atmosphere of argon.
The reaction mixture was poured into 10 mL saturated NH

4
Cl solution and extracted three
times with 10 mL of Et
2
O. The combined organic layers were washed with 10 mL water and
brine. The organic layer was dried over Na
2
SO
4
and the solvent was removed on a rotary
evaporator. The resulting crude material (31 mg) was not purified as the obtained product
looked unstable since the colour changed from yellow to dark blue when evaporated to
dryness.
It should be noted that all calculations are based on the theoretical yield of the previous
reaction. To a solution of tert-alcohol 5-21 (31.0 mg, 0.092 mmol) in freshly distilled THF (3
mL) was added Burgess reagent (44.0 mg, 0.185 mmol). The reaction mixture was stirred
under an inert atmosphere of argon for 20 h. The reaction was poured into 15 mL of water and
extracted three times with 10 mL of Et
2
O. The combined organic layers were washed with 10
mL of water and brine. The organic layer was dried over Na
2
SO
4
and the solvent was
removed on a rotary evaporator. The resulting crude product was purified by preparative
O
O
O
O

5-22
MeO
MeO
OMe
MeO