Total synthesis of (-)-basiliskamide A and NMR studies on the conversion of basiliskamide A to basiliskamide B

Article abstract of DOI:10.1590/S0103-50532010001000030

We describe herein our approach to the total synthesis of the antifungal polyketide (-)-basiliskamide A, as well as ¹H NMR studies on the migration of the cinnamoyl side chain of basiliskamide A to form basiliskamide B in CDCl₃ solution.

Full text of DOI:10.1590/S0103-50532010001000030

J. Braz. Chem. Soc., Vol. 21, No. 10, 2012-2016, 2010.
Printed in Brazil - ©2010 Sociedade Brasileira de Química
0103 - 5053 $6.00+0.00
Total Synthesis of (-)-Basiliskamide A and NMR Studies on the Conversion of
Basiliskamide A to Basiliskamide B
Luiz C. Dias* and Caroline C. S. Gonçalves
Instituto de Química, Universidade Estadual de Campinas, CP 6154,
13083-970 Campinas-SP, Brazil
Descrevemos neste trabalho nossa rota sintética para obtenção do policetídeo antifúngico
(-)-basiliskamidaA, assim como estudos de RMN de 1H relacionados a migração da cadeia lateral
cinamoíla da basiliskamida A para formar a basiliskamida B em CDCl3.
We describe herein our approach to the total synthesis of the antifungal polyketide
(-)-basiliskamide A, as well as 1H NMR studies on the migration of the cinnamoyl side chain of
basiliskamide A to form basiliskamide B in CDCl3 solution.
Keywords: antifungal polyketides, Stille cross-coupling, aldol reaction, NMR studies
Introduction
Results and Discussion
The polyketides basiliskamides A (1) and B (2) were
isolated from the marine bacterium PNG-276 from the
coast of Papua New Guinea (Figure 1).1,2 These antifungal
polyketides show potent in vitro activity against Candida
albicans and Aspergillus fumigatus,1 as well as at least
4-fold less cytotoxicity for normal human fibroblast
cells when compared to amphotericin B.1,3 The relative
configurations of basiliskamides A (1) and B (2) were
proposed by Andersen and co-workers1 and the absolute
configurations have been confirmed by total synthesis.4
We have recently concluded the total synthesis of
basiliskamide B.5 As the natural supply of basiliskamide
A is restricted, and attracted by its potent cytotoxicity, we
initiated a project directed towards an efficient and flexible
total synthesis, in order to provide further material for
more extensive biological studies, along with access to
novel analogs.6
Our approach for the preparation of (-)-basiliskamide
A (1) began with the synthesis of vinyl iodide 4, prepared
in 7 steps and 19.1% overall yield from ethylketone 3
(Scheme 1).5,7
The next step involved a Stille cross-coupling
reaction between Z-vinylstannane 58 and E-vinyl iodide 4
(Scheme 2). This was accomplished by treatment of 4 and 5
in DMF with catalytic amounts of Pd(MeCN)2Cl2 at 50 oC,
providing 6 in 60% yield after purification by silica-gel
column chromatography.At this point only four synthetic
operations remained to conclude the total synthesis of
(-)-basiliskamideA. Removal of the isopropylidene acetal
protecting group in 6 with 80% AcOH provided diol 7.
Selective protection of the less hindered oxygen with
TES chloride in the presence of pyridine gave alcohol
8 (67% yield, 2 steps).9 Treatment of secondary alcohol
O
O
Ph
O
OH
OH
O
Ph
Me
H2N
H2N
Me
Me Me
basiliskamide B (2)
Me Me
basiliskamide A (1)
O
O
Figure 1. Basiliskamides A and B.
*e-mail: ldias@iqm.unicamp.br

Vol. 21, No. 10, 2010
Dias and Gonçalves
2013
Me Me
from the more hindered oxygen at C9 in basiliskamide A
to the less hindered oxygen at C7.
O
O
O
OPMB
Ref. 5
I
Me
1
In the H NMR spectrum of basiliskamide A (1), the
9
Me
9
5
3
signal at d 3.63 ppm (dt, J 3.5 and 10.0 Hz) is attributed to
the hydrogen H7. In the 1H NMR spectrum of basiliskamide
B the signal at d 3.35 ppm (dd, J 2.5 and 9.5 Hz) refers to
the hydrogen H9 (Figure 2).
Me Me
Me
4 (E:Z = 88:12)
Scheme 1. Synthesis of vinyl iodide 4 from of ethylketone 3.
After 24 h, the 1H NMR spectrum of basiliskamideA (1)
shows a new signal at d 3.35 ppm, which corresponds to the
hydrogenH9ofbasiliskamideB(Figure3).After20days, we
can observe that the signal at d 3.35 ppm increases leading to
a 1.00:0.45 ratio of basiliskamideA (1) and basiliskamide B
(2), respectively. This clearly shows that the migration of the
cinnamoyl side chain is occurring and that it is possible that
basiliskamide B is an artifact of basiliskamide A.10
8 with E-cinnamoyl chloride in the presence of DMAP
and Et3N gave ester 9, which, after treatment with HF in
acetonitrile, provided (-)-basiliskamide A in 42% for the
four-step sequence.
The spectroscopic and physical data (1H and 13C NMR,
IR, [a]D, Rf) for synthetic (-)-basiliskamide A were
identical in all respects with the published data for the
natural product.1,4
Conclusions
NMR studies
In summary, a highly convergent and efficient total
synthesis of (-)-basiliskamide A has been accomplished.
The synthesis required 15 steps from ethylketone 3 and
produced the desired product in 3.2% overall yield. This
approach compares very well with the published routes to
(-)-basiliskamide A4 and the synthetic strategy presented
here is, in principle, readily applicable for the preparation
of additional analogues.
At this point, we decided to investigate the possibility
of basiliskamide B being produced by cinnamoyl side
chain migration from basiliskamide A. To this end, we
did an NMR study to verify whether the conversion of
basiliskamide A to basiliskamide B in mild acidic CDCl3
solution was possible or not (Scheme 3). This conversion
would occur through migration of the cinnamoyl side chain
O
SnBu3
H
Me Me
H2N
1
5
O
O
+
80% AcOH
60 oC, 3 h
Pd(MeCN)2Cl2
H2N
1
Me Me
Me
5
9
DMF, 50 oC
O
Me Me
6
O
O
60%
I
Me
9
4
Me Me
TES
O
OH
OH OH
TESCl, pyridine
25 oC, 67%
3
H2N
1
1
H2N
9
7
Me
Me
5
9
4
Me Me
O
Me Me
8
7
O
(2 steps)
O
TES
O
O
Ph
Me
(E)-cinnamoyl chloride
HF, CH3CN
42% (4 steps)
H2N
1
9
7
DMAP, Et3N, CH2Cl2
9
Me Me
O
O
OH
O
Ph
Me
H2N
1
7
9
Me Me
basiliskamide A (1)
O
Scheme 2. Total synthesis of (-)-basiliskamide A.

2014
Total Synthesis of (–)-Basiliskamide A and NMR Studies on the Conversion of Basiliskamide A to B
J. Braz. Chem. Soc.
O
O
O
O
OH
OH
O
Ph
Ph
Ph
Ph
O
OH
O
O
OH
H+
H
1
1
1
1
H N
H2N
H N
H2N
Me
Me
9
9
Me
Me
9
9
5
5
5
5
CDCl
CDCl3
Me Me
Me Me
basiliskamide A (1)
basiliskamide A (1)
Me Me
Me Me
O
O
O
O
solution
solution
basiliskamide B (2)
basiliskamide B (2)
#
#
H
H
H
H
O
O
R1 =
R =
NH
NH2
H
H
forming bond
breaking bond
breaking bond
forming bond
7
R1
O
7
Ph
Ph
O
O
O
R
R2 =
Me
Me
R =
9
9
O
O
Me
Me
R2
H
H
R
Me
Me
H
H
Scheme 3. Cinnamoyl side chain migration of basiliskamide A.
Figure 2. Chemical shifts in the 1H NMR spectrum (CDCl3, 500 MHz) of H7 in basiliskamide A (1) and H9 in basiliskamide B (2).
Experimental
J 5.3 Hz); 4.7 (d, 1H, J 4.7 Hz); 5.58 (d, 1H, J 5.6 Hz); 6.03
(dt, 1H, J 6.0 Hz); 6.37 (t, 1H, J 11.5 Hz); 6.86 (brs, 1H);
7.37 (brs, 1H);7.45 (dd, 1H, J 11.5 e 15.5 Hz). 13C NMR
(DMSO-d6, 62.5 MHz): d 11.3; 12.4; 12.5; 27.22; 35.9; 36.8;
41.9; 71.9; 74.8; 119.6; 128.5; 141.2; 141.3; 168.1. IR (film)
(-)-Basiliskamide A (1)
The diene 6 (68.5 mg, 0.23 mmol) was dissolved in 80%
acetic acid (5 mL). The reaction was protected from light
and stirred at 60 oC for 3 h. The reaction was then allowed
to reach ambient temperature and adjusted to pH 7.0 with
NH4OH. The aqueous phase was extracted with EtOAc
(2 × 10 mL), the combined organic extracts were dried over
MgSO4, filtered and concentrated under reduced pressure
to give the corresponding diol 7. Rf = 0.15 (hexane:EtOAc,
50:50). [a]D25 = +15 (c = 0.35, CHCl3). 1H NMR (DMSO-d6,
250 MHz): d 0.69 (d, 3H, J 7.0 Hz); 0.73 (d, 3H, J 6.3 Hz);
0.84 (t, 3H, J 7.3 Hz); 1.35 (m, 3H), 1.61 (m, 1H); 2.05 (m,
1H); 2.28 (m, 1H); 3.24 (m, 1H); 3.81 (m, 1H); 4.49 (d, 1H,
n
max/cm-1:3350, 2964, 2930, 2871, 1666, 1454, 1327. HRMS:
[C14H26NO3+]: expected: 256.1907; observed: 256.1913.
A solution of the corresponding crude diol 7 obtained
before (44.8 mg; 0.18 mmol) in pyridine (3 mL) was treated
with TESCl (0.033 mL; 0.19 mmol) at 0 oC, and stirred at
o
25 C for 2 h. The reaction was quenched with aqueous
saturated NaHCO3 solution and extracted with EtOAc
providing alcohol 8. Rf = 0.4 (hexane:EtOAc, 50:50).
1H NMR (C6D6, 250 MHz): d 0.73 (q, 6H, J 8 Hz); 0.84
(d, 3H, J 6.8 Hz); 1.01 (m, 6H); 1.12 (t, 9H, J 8 Hz); 1.49
(m, 3H); 2.02 (m, 1H); 2.43 (t, 2H, J 6.3 Hz); 2.67 (brd,

Vol. 21, No. 10, 2010
Dias and Gonçalves
2015
Figure 3. Partial 1H NMR spectrum (CDCl3, 500 MHz) showing the migration of the cinnamoyl side chain after 24 h and after 20 days.
1H, J 3.3 Hz); 3.44 (brd, 1H, J 8.5 Hz); 4.23 (q, 1H, J 5.3
Hz); 4.72 (brs, 1H); 5.19 (d, 1H, J 11.3 Hz); 5.59 (brs, 1H);
6.25 (dt, 1H, J 7.3 e 15.5 Hz); 6.39 (t, 1H, J 11.3 Hz); 8.17
(dd, 1H, J 11.5 e 15.3 Hz). 13C NMR (C6D6, 62.5 MHz):
d 5.5; 7.2; 11.3; 11.8; 12.4; 27.6; 36.8; 37.2; 42.1; 75.2;
75.6; 118.2; 129.6; 141.1; 142.6; 168.1.
130.4; 134.0; 140.56; 140.58; 144.6; 166.1; 167.5. IR (film)
n
max/cm-1: 3367, 2966, 2936, 1701, 1670, 1588.
The crude compound 9 (0.029 mmol) was treated
with 0.4 mL of a solution of HF (40% aqueous solution):
CH3CN (1:18). After 10 min at r.t. the reaction was
quenched with NaHCO3 (4 mg) and stirred for 10 min,
filtered and concentrated in vacuo. Purification by flash
column chromatography (EtOAc:CH2Cl2, 4:2) afforded
(-)-basiliskamide A (1) (4.6 mg, 42% yield, 4 steps).
Rf = 0.6 (EtOAc:CH2Cl2, 40:10). 1H NMR (DMSO-d6, 5000
MHz): d 7.72 (2H, m); 7.66 (1H, d, 16.0 Hz); 7.41 (3H, m);
7.41 (3H, m); 7.39 (1H, m); 7.33 (1H, brs); 6.84 (1H, brs);
6.62 (1H, d, 16.0 Hz); 6.31 (1H, apt, 11.5 Hz); 5.91 (1H, dt,
7.4 and 14.9 Hz); 5.55 (1H, d, 11.5 Hz); 4.92 (1H, dd, 2.6
and 9.5 Hz); 4.58 (1H, d, 5.4 Hz); 3.48 (1H, m); 2.28 (1H,
m); 2.02 (1H, m); 2.02 (1H, m), 1.67 (1H, m); 1.25 (1H,
m); 1.11 (1H, m); 0.89 (3H, d, 6.6 Hz); 0.87 (3H, t, 7.7 Hz);
0.84 (3H, d, 7.1 Hz) ppm. 13C NMR (DMSO-d6, 125 MHz):
d 167.5; 166.1; 144.6; 140.56; 140.51; 134.0; 130.4; 128.9;
128.4; 128.3; 119.4; 118.0; 76.3; 69.7; 40.8; 35.5; 34.7; 26.4;
12.8; 11.7; 10.1 ppm.
The crude alcohol 8 (0.029 mmol) in CH2Cl2 (0.7 mL)
was treated with Et3N (0.034 mL; 0.24 mmol) and DMAP
(1.7 mg, 0.014 mmol) and cooled to 0 oC. The solution was
treated with (E)-cinnamoyl chloride (0.02 g; 0.12 mmol).
The reaction was protected from light and stirred at ambient
temperature for 18 h, and the reaction was then quenched
with water. The aqueous phase was extracted with CH2Cl2
and the solvent was removed under reduced pressure
to provide ester 9. Rf = 0.55 (EtOAc:CH2Cl2, 40:10).
[a]D25 = -77 (c 0.26, MeOH). 1H NMR (CDCl3, 500 MHz):
d 0.83 (d, 3H, J 7.0 Hz); 0.84 (d, 3H, J 7.0 Hz); 0.87 (t, 3H,
J 7.5 Hz); 0.90 (d, 3H, J 7.0 Hz); 1.11 (m, 1H) 1.25 (m,
1H); 1.67 (m, 1H); 1.99 (m, 1H); 2.06 (m, 1H); 2.28 (m,
1H); 3.49 (m, 1H); 4.57 (d, 1H, J 5.0 Hz); 4.92 (dd, 1H;
J 2.0 e 9.5 Hz); 5.55 (d, 1H, J 11.0 Hz); 5.91 (dt, 1H, J 7.0 e
15.0 Hz); 6.31 (brt, 1H, J 11.0 Hz); 6.61 (d, 1H, J 16.0 Hz);
6.83 (s, 1H); 7.31 (s, 1H); 7.40 (dd, 1H, J 11.0 e 15.0 Hz);
7.41 (m, 2H); 7.65 (d, 1H, J 16.0 Hz); 7.71 (m, 2H).
13C NMR (CDCl3, 100 MHz): d 10.1; 11.6; 12.8; 26.4; 34.7;
35.5; 40.8; 69.7; 76.3; 118.0; 119.3; 128.2; 128.4; 128.9;
Supplementary Information
Supplementary data are available free of charge at
http://jbcs.sbq.org.br, as a PDF file.

2016
Total Synthesis of (–)-Basiliskamide A and NMR Studies on the Conversion of Basiliskamide A to B
J. Braz. Chem. Soc.
Acknowledgments
Donate, P. M.; J. Braz. Chem. Soc. 2009, 20, 888;Abaee, M. S.;
Mojtahedi, M. M.; Forghani, S.; Ghandchi, N. M.; Forouzani,
M.; Sharifi, R.; Chaharnazm, B.; J. Braz. Chem. Soc. 2009, 20,
1895.
We are grateful to FAEP-Unicamp, FAPESP
(Fundação de Amparo à Pesquisa do Estado de São
Paulo), CNPq (Conselho Nacional de Desenvolvimento
Científico e Tecnológico) and INCT-INOFAR Proc. CNPq
573.564/2008-6 for financial support. We also thank Prof.
Carol H. Collins (Unicamp), for helpful suggestions about
English grammar and style, Leonardo José Steil (UFABC)
for helpful comments and Professor Carlos Roque Duarte
Correia (Unicamp) for suggestions and comments about
the NMR studies.
7. The numbering of 1 follows that suggested in reference 1.
8. Stille, J. K.; Groh, B. L.; J. Am. Chem. Soc. 1987, 109, 813;
Espinet, P.; Echavarren, A. M.; Angew. Chem. Int. Ed. 2004,
43, 4704; Farina, V.; Pure Appl. Chem. 1996, 68, 73; Farina,
V.; Krishnan, B.; J. Am. Chem. Soc. 1991, 113, 9585; Singh,
R.; Sharma, M.; Mamgaun, R.; Rawat, D. D.; J. Braz. Chem.
Soc. 2008, 19, 357.
9. Dias, L. C.; de Sousa, M. A.; Tetrahedron Lett. 2003, 44, 5625;
Dias, L. C.; de Oliveira, L. G.; de Sousa, M.A.; Org. Lett. 2003,
5, 265; Dias, L. C.; Meira, P. R. R.; Tetrahedron Lett. 2002,
43, 185; Dias, L. C.; Meira, P. R. R.; J. Org. Chem. 2005, 70,
4762; Dias, L. C.; de Oliveira, L. G.;Vilcachagua, J. D.; Nigsch,
F.; J. Org. Chem. 2005, 70, 2225; Dias, L. C.; Ferreira, E.;
Tetrahedron Lett. 2001, 42, 7159; Dias, L. C.; Ferreira, A. A.;
Diaz, G.; Synlett 2002, 1845; Dias, L. C.; Diaz, G.; Ferreira, A.
A.; Meira, P. R. R.; Ferreira, E.; Synthesis 2003, 4, 603; Dias, L.
C.; Meira, P. R. R.; Ferreira, E.; Org. Lett. 1999, 1, 1335; Dias,
L. C.; Giacomini, R.; Tetrahedron Lett. 1998, 39, 5343; Dias,
L. C.; Meira, P. R. R.; Synlett 2000, 37; Dias, L. C.; Rittner, R.;
J. Phys. Chem. A. 2005, 109, 6077.
References
1. Barsby, T.; Kelly, M. T.; Andersen R. J.; J. Nat. Prod. 2002,
65, 1447; Kelly, M. T.; Anderson, R. J.; Barsby, T.; US Patent
2005/0277779 A1, 2005.
2. Mayer, A. M. S.; Hamann, M. T.; Comp. Biochem. Physiol.
2005, 140C, 265.
3. Blunt, J. W.; Copp, B. R.; Munro, M. H. G.; Northcote, P.
T.; Prinsep, M. R.; Nat. Prod. Rep. 2004, 21, 1; Delgado, V.;
Armstrong, V; Cortés, M.; Barrero, A. F.; J. Braz. Chem. Soc.
2008, 19, 1258.
4. Lipomi, D. J.; Langille, N. F.; Panek, J. S.; Org. Lett. 2004,
6, 3533; Yadav, J. S.; Rao, P. P; Reddy, M. S.; Prasad, A. R.;
Tetrahedron Lett. 2008, 49, 5427.
10. When submitting (-)-basiliskamide B to the same experiment
we can not observe the signal at d 3.63 ppm (dt, J 3.5 and
10.0 Hz) that corresponds to hydrogen H7 of basiliskamide A.
However, the formation of another compound that shows three
well defined signals (d 3.65, 4.94 and 5.04 ppm) was observed.
5. Dias, L. C.; Gonçalves, C. C. S.; Adv. Synth. Catal. 2008, 350,
1017.
6. Ermolenko, M. S.; Tetrahedron Lett. 1996, 37, 6711; Sugawara,
T.; Shibazaki, M.; Nakahara, H.; Suzuki, K.; J. Antibiot.
1996, 49, 345; Okada, Y.; Matsunaga, S.; van Soest, R. W.
M.; Fusetani, N.; Org. Lett. 2002, 4, 3039; Mohapatra, D.
K.; Chaudhuri, S. R.; Sahoo, G.; Gurjar, M. K.; Tetrahedron:
Asymmetry 2006, 17, 2609; Frederico, D.; Constantino, M. G.;
Submitted: May 4, 2010
Published online: August 3, 2010
FAPESP has sponsored the publication of this article.

J. Braz. Chem. Soc., Vol. 21, No. 10, S1-S6, 2010.
Printed in Brazil - ©2010 Sociedade Brasileira de Química
0103 - 5053 $6.00+0.00
Total Synthesis of (-)-Basiliskamide A and NMR Studies on the Conversion of
Basiliskamide A to Basiliskamide B
Luiz C. Dias* and Caroline C. S. Gonçalves
Instituto de Química, Universidade Estadual de Campinas, CP 6154,
13084-971 Campinas-SP, Brazil
Figure S1. 1H NMR of acetonide 6 (DMSO-d6, 250 MHz).
*e-mail: ldias@iqm.unicamp.br

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Total Synthesis of (–)-Basiliskamide A and NMR Studies on the Conversion of Basiliskamide A to B
J. Braz. Chem. Soc.
Figure S2. 13C NMR of acetonide 6 (DMSO-d6, 62.5 MHz).
Figure S3. IR of acetonide 6.

Vol. 21, No. 10, 2010
Dias and Gonçalves
S3
Figure S4. 1H NMR of diol 7 (DMSO-d6, 250 MHz).
Figure S5. 13C NMR of diol 7 (DMSO-d6, 62.5 MHz).

S4
Total Synthesis of (–)-Basiliskamide A and NMR Studies on the Conversion of Basiliskamide A to B
J. Braz. Chem. Soc.
Figure S6. IR of diol 7.
Figure S7. HRMS of diol 7.

Vol. 21, No. 10, 2010
Dias and Gonçalves
S5
Figure S8. 1H NMR of basiliskamide A (1), (DMSO-d6, 500 MHz).
Figure S9. 13C NMR of basiliskamide A (1), (DMSO-d6, 125 MHz).

S6
Total Synthesis of (–)-Basiliskamide A and NMR Studies on the Conversion of Basiliskamide A to B
J. Braz. Chem. Soc.
Figure S10. IR of basiliskamide A (1).
Table 1. Comparison of 1H and 13C NMR data for natural1 and our synthetic basiliskamide A (DMSO-d6)
1H NMR (400 MHz)
d/ppm (number of hydrogens,
multiplicity, coupling constant)
Natural
1H NMR (500 MHz)
d/ppm (number of hydrogens,
multiplicity, coupling constant)
Synthetic
13C NMR (100 MHz)1
d (ppm)
13C NMR (125 MHz)1
d (ppm)
Natural
Synthetic
0.84 (3H, d, 7.0 Hz)
0.87 (3H, t, 7.5 Hz)
0.90 (3H, d, 7.0 Hz)
1.11 (1H, m)
0.84 (3H, d, 7.1 Hz)
0.87 (3H, t, 7.7 Hz)
0.89 (3H, d, 6.6 Hz)
1.11 (1H, m)
10.1
11.6
12.8
26.4
34.7
35.5
40.7
69.6
76.3
118.0
119.3
128.2
128.4
128.9
130.4
134.0
140.5
-
10.1
11.7
12.8
26.4
1.25 (1H, m)
1.25 (1H, m)
34.7
1.67 (1H, m)
1.67 (1H, m)
35.5
1.99 (1H, m)
2.02 (1H, m)
40.8
2.06 (1H, m)
2.04 (1H, m)
69.7
2.28 (1H, m)
2.28 (1H, m)
76.3
3.49 (1H, m)
3.48 (1H, m)
118.0
119.4
128.3
128.4
128.9
130.4
134.0
140.51
140.56
144.6
166.1
167.5
-
4.57 (1H, d, 5.0 Hz)
4.92 (1H, dd, 2.0 and 9.5 Hz)
5.55 (1H, d, 11.0 Hz)
5.91 (1H, dt, 7.0 and 15.0 Hz)
6.31 (1H, dd, 11.0 and 11.0 Hz)
6.61 (1H, d, 16.0 Hz)
6.83 (1H, s)
4.58 (1H, d, 5.4 Hz)
4.92 (1H, dd, 2.6 and 9.5 Hz)
5.55 (1H, d, 11.5 Hz)
5.91 (1H, dt, 7.4 and 14.9 Hz)
6.31 (1H, apt, 11.3 Hz)
6.62 (1H, d, 15.9 Hz)
6.84 (1H, brs)
7.31 (1H, s)
7.33 (1H, brs)
7.40 (1H, dd, 11.0 and 15.0 Hz)
7.40 (1H, m)
7.39 (1H, m)
144.6
166.0
167.4
-
7.41 (3H, m)
7.41 (2H, m)
-
7.65 (1H, d, 16.0 Hz)
7.71 (2H, m)
7.66 (1H, d, 16.0 Hz)
7.72 (2H, m)
-
-
1. Barsby, T.; Kelly, M. T.; Andersen R. J.; J. Nat. Prod. 2002, 65, 1447; Kelly, M. T.; Anderson, R. J.; Barsby, T.; US Patent 2005/0277779 A1, 2005.