Structure elucidation and synthesis of lycoposerramine-B, a novel oxime-containing lycopodium alkaloid from Lycopodium serratum thunb

Article abstract of DOI:10.1021/jo0483825

(Chemical Equation Presented) A new alkaloid, lycoposerramine-B (1), containing an oxime function, was isolated from the club moss Lycopodium serratum Thunb. The structure of 1 was elucidated by spectroscopic analysis, including J-resolved HMBC spectroscopy, and confirmed by its synthesis from the known alkaloid, serratinine (3).

Full text of DOI:10.1021/jo0483825

Structure Elucidation and Synthesis of Lycoposerramine-B, a
Novel Oxime-Containing Lycopodium Alkaloid from Lycopodium
serratum Thunb.
†
†
†
§
|
Kazuaki Katakawa, Mariko Kitajima, Norio Aimi, Hiroko Seki, Kentaro Yamaguchi,
⊥
‡
,†
Kazuo Furihata, Takashi Harayama, and Hiromitsu Takayama*
Graduate School of Pharmaceutical Sciences, Chiba University, 1-33 Yayoi-cho, Inage-ku,
Chiba 263-8522, Japan, Analysis Center, Chiba University, 1-33 Yayoi-cho, Inage-ku,
Chiba 263-8522, Japan, Faculty of Pharmaceutical Sciences at Kagawa Campus, Tokushima Bunri
University, 1314-1 Shido, Sanuki, Kagawa 769-2193, Japan, Graduate School of Agricultural and Life
Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan, and Faculty of
Pharmaceutical Sciences, Okayama University, 1-1-1 Tsushima-naka, Okayama 700-8520, Japan
takayama@p.chiba-u.ac.jp
Received September 14, 2004
A new alkaloid, lycoposerramine-B (1), containing an oxime function, was isolated from the club
moss Lycopodium serratum Thunb. The structure of 1 was elucidated by spectroscopic analysis,
including J-resolved HMBC spectroscopy, and confirmed by its synthesis from the known alkaloid,
serratinine (3).
number of new alkaloids from L. serratum.4 Further
purification of the alkaloidal fraction of this plant has
led to the isolation of a new base named lycopo-
serramine-B (1), which was the first example of a
Lycopodium alkaloid having an oxime function in the
molecule. In this paper, we describe structure elucidation
by means of spectroscopic analysis and the chemical
transformation from a known alkaloid, serratinine (3).
-6
Introduction
The genus Lycopodium, which produces structurally
1
complex alkaloids and potent acetylcholine esterase3
2
inhibitors, has been extensively studied by many groups.
In our continuing chemical studies on the structurally
unique alkaloids of Lycopodium, we have isolated a
*
To whom correspondence should be addressed. Phone and Fax:
Results and Discussion
+
81-43-290-2901.
†
Graduate School of Pharmaceutical Sciences, Chiba University.
1
. Isolation and Structure Elucidation of Lyco-
§
Analysis Center, Chiba University.
|
poserramine-B by Spectroscopic Analysis. The crude
Tokushima Bunri University.
⊥
The University of Tokyo.
base fraction obtained by means of a previously reported
procedure was purified by repeated chromatography over
‡
Okayama University.
6
(1) For pertinent reviews, see: (a) Ayer, W. A.; Trifonov, L. S.
Lycopodium alkaloids. In The Alkaloids; Cordell, G. A., Brossi, A., Eds.;
Academic Press: San Diego, CA, 1994; Vol. 45, Chapter 3. (b) Ayer,
W. A. Nat. Prod. Rep. 1991, 8, 455-463.
2
SiO gel to afford a new alkaloid, lycoposerramine-B (1,
0
.07% yield based on the crude base).
Compound 1, named lycoposerramine-B, was obtained
(2) (a) Kozikowski, A. P.; T u¨ ckmantel, W. Acc. Chem. Res. 1999, 32,
6
41-650. (b) Wong, D. M.; Greenblatt, H. M.; Dvir, H.; Carlier. P. R.;
Han, Y.-F.; Pang, Y.-P.; Silman, I.; Sussman, J. L. J. Am. Chem. Soc.
003, 125, 363-373. (c) Xu, Y.; Shen, J.; Luo, X.; Silman, I.; Sussman,
J. L.; Chen, K.; Jiang, H. J. Am. Chem. Soc. 2003, 125, 11340-11349.
3) (a) Hirasawa, Y.; Morita, H.; Kobayashi, J. Org. Lett. 2004, 6,
389-3391 and references therein. (b) Tori, M.; Shimoji, T.; Shimura,
E.; Takaoka, S.; Nakashima, K.; Sono, M.; Ayer, W. A. Phytochemistry
as a colorless amorphous powder. High-resolution FAB-
2
(4) Takayama, H.; Katakawa, K.; Kitajima, M.; Seki, H.; Yamaguchi,
K.; Aimi, N. Org. Lett. 2001, 3, 4165-4167. Takayama, H.; Katakawa,
K.; Kitajima, M.; Seki, H.; Yamaguchi, K.; Aimi, N. Org. Lett. 2002, 4,
1243.
(5) Takayama, H.; Katakawa, K.; Kitajima, M.; Yamaguchi, K.; Aimi,
N. Tetrahedron Lett. 2002, 43, 8307-8311.
(6) Takayama, H.; Katakawa, K.; Kitajima, M.; Yamaguchi, K.; Aimi,
N. Chem. Pharm. Bull. 2003, 51, 1163-1169.
(
3
2
000, 53, 503-509 and references therein. (c) Tan, C.-H.; Ma, X.-Q.;
Chen, G.-F.; Zhu, D.-Y. Can. J. Chem. 2003, 81, 315-318 and
references therein.
10.1021/jo0483825 CCC: $30.25 © 2005 American Chemical Society
658
J. Org. Chem. 2005, 70, 658-663
Published on Web 12/29/2004

Synthesis of Lycoposerramine-B
TABLE 1. 1H and 13C Data of Lycoposerramine-B (1) in
CDCl3
δ
H
δ
C
HMBC (H to C)
1
1
2
2
3
3
4
5
6
6
7
8
9
9
1
1
1
1
1
1
1
1
1
1
a
b
a
b
a
b
2.03 (1H, m)
48.5 C-2, 9
27.5
2.66 (1H, dd, 13.4, 13.4)
1.46 (1H, m)
1.69 (1H, m)
1.28 (1H, br d, 14.4)
2.00 (1H, m)
25.5a
C-2, 4, 12
FIGURE 2. J-resolved HMBC analysis for 1.
3.18 (1H, d-like, 2.8)
42.9 C-2, 3, 5, 6, 11, 12, 13
169.6
28.7 C-4, 5, 7, 8, 12
C-4, 5, 7, 12
42.9 C-5, 6, 12, 13
31.6 C-6, 7, 12, 14, 15, 16
55.1
a
b
2.20 (1H, m)
peaks between the N-methyl proton (δ 2.27, 3H, s) and
the two terminal carbons of fragments a (δ 48.5, C-1) and
c (δ 55.1, C-9) indicated that these two fragments and
the methyl group were connected by a nitrogen atom.
HMBC correlations between two protons (δ 3.18, H-4 and
δ 2.41, H-7) and quaternary carbon (δ 61.7, C-12) and
between methine proton (δ 3.18, H-4) and methylene
carbon (δ 25.6, C-11) implied these three fragments (a,
b, and c) attached to the quaternary carbon (δ 61.7,
C-12). HMBC correlations between three protons (δ 3.18,
H-4; δ 2.41, H-7; and δ 2.27, H-14) and one carbonyl
carbon (δ 213.8, C-13) pointed to the presence of a
cyclohexanone ring system. Further HMBC correlations
between methylene protons (δ 2.20, 2.54, H-6) as well as
two methine protons (δ 2.41, H-7 and δ 3.18, H-4) and
the carbon signal at δ 169.6 implied that fragments a
and b were attached to a particular carbon ascribable to
the oxime at both terminal carbons (C-4 and C-6). All of
these data indicated that lycoposerramine-B (1) had a
fundamental skeleton of fawcettimine (2)7 with the keto-
amine form (see Scheme 3).
2.54 (1H, ddd, 1.1, 9.5, 19.0)
2.41 (1H, m)
1.73 (2H, m)
a
b
2.27 (1H, m)
2.31 (1H, m)
0a
0b
1a
1b
2
1.20 (1H, m)
21.4
1.36 (1H, m)
25.6a C-4, 7, 9, 10, 12, 13
C-9, 10, 12, 13
61.7
2.00 (1H, m)
2.20 (1H, m)
3
213.8
4a
4b
5
2.20 (1H, m)
2.27 (1H, m)
2.10 (1H, m)
1.03 (3H, d, 6.4)
2.27 (3H, s)
46.8 C-8, 12, 13, 15, 16
C-8, 13, 15, 16
29.9
22.5 C-8, 14, 15
44.4 C-1, 9
6
N-CH
3
a
Interchangeable
,8
The stereochemistry at C-7, -12, and -15 was assumed
to be the same as those in fawcettimine (2) based on the
biogenetic speculation described below. The configuration
9
at C-4 was inferred from J-resolved HMBC spectral data
3
(
Figure 2). The large coupling constants JH4-C7 (5.2 Hz)
3
3
and JH7-C13 (6.3 Hz) as well as the small values JH4-C13
e3 Hz) and JH7-C4 (0 Hz) are consistent with H-4â
3
(
configuration.
. Synthesis of 1 from Serratinine. To confirm the
structure of 1 that was inferred by spectroscopic analysis,
2
1
0
we attempted its synthesis from serratinine (3), the
(
7) (a) Burnell, R. H.; Mootoo, B. S. Can. J. Chem. 1961, 39, 1090-
FIGURE 1. Structure and selected 2D NMR data for 1.
MS gave m/z 293.2227 [(M + H)+ (∆ -0.2 mmu)] and
1
093. (b) Inubushi, Y.; Ishii, H.; Harayama, T.; Burnell, R. H.; Ayer,
W. A.; Altenkirk, B. Tetrahedron Lett. 1967, 8, 1069-1072. (c)
Harayama, T.; Takatani, M.; Inubushi, Y. Chem. Pharm. Bull. 1980,
28, 2394-2402. (d) Inubushi, Y.; Harayama, T. Chem. Pharm. Bull.
established the molecular formula as C17
28 2 2
H N O . The
1
981, 29, 3418-3421.
(
IR spectrum indicated the presence of one ketone (1699
8) (a) Heathcock, C. H.; Smith, K. M.; Blumenkopf, T. A. J. Am.
-
1
-1
1
13
cm ) and one hydroxyl group (3279 cm ). H and
C
Chem. Soc. 1986, 108, 5022-5024. (b) Heathcock, C. H.; Blumenkopf,
T. A.; Smith, K. M. J. Org. Chem. 1989, 54, 1548-1562.
NMR (Table 1) spectra showed the presence of one ketone
2
(9) Furihata, K.; Seto, H. Tetrahedron Lett. 1999, 40, 6271-6275.
(
δ 213.8), one sp carbon probably ascribable to an imine
(10) (a) Inubushi, Y.; Ishii, H.; Yasui, B.; Hashimoto, M.; Harayama,
function (δ 169.6), one quaternary carbon (δ 61.7), one
methyl group (δ 2.27, 3H, s) on a nitrogen atom, and one
secondary methyl group (δ 1.03, 3H, d, J ) 6.4 Hz),
besides three methine and nine methylene carbons. The
presence of an oxime function was deduced from the
T. Tetrahedron Lett. 1966, 7, 1537-1549. (b) Inubushi, Y.; Ishii, H.;
Yasui, B.; Harayama, T. Tetrahedron Lett. 1966, 7, 1551-1559. (c)
Inubushi, Y.; Ishii, H.; Yasui, B.; Hashimoto, M.; Harayama, T. Chem.
Pharm. Bull. 1968, 16, 82-91. (d) Inubushi, Y.; Ishii, H.; Yasui, B.;
Hashimoto, M.; Harayama, T. Chem. Pharm. Bull. 1968, 16, 92-100.
(
e) Inubushi, Y.; Ishii, H.; Yasui, B.; Harayama, T. Chem. Pharm. Bull.
+
1968, 16, 101-112. (f) Inubushi, Y.; Ibuka, T.; Harayama, T.; Ishii, H.
Tetrahedron 1968, 24, 3541-3556. (g) Nishio, K.; Fujiwara, T.; Tomita,
K.; Ishii, H.; Inubushi, Y.; Harayama, T. Tetrahedron Lett. 1969, 10,
intense fragment peak at m/z 275 (M - OH) and the
2
chemical shift of the isolated sp carbon (δ
c
169.6), and
861-864. (h) Ishii, H.; Yasui, B.; Nishino, R.; Harayama, T.; Inubushi,
by taking the molecular formula (C17
H N O ) into con-
28 2 2
Y. Chem. Pharm. Bull. 1970, 18, 1880-1888. (i) Harayama, T.; Ohtani,
M.; Oki, M.; Inubushi, Y. Chem. Pharm. Bull. 1975, 23, 1511-1515.
(j) Zhou, B.-N.; Zhu, D.-Y.; Huang, M.-F.; Lin, L.-J.; Lin, L.-Z.; Han,
X.-Y.; Cordell, G. A. Phytochemistry 1993, 34, 1425-1428. (k) Morita,
H.; Arisaka, M.; Yoshida, N.; Kobayashi, J. J. Org. Chem. 2000, 65,
1
1
sideration. H- H COSY and HMQC (Figure 1) analyses
indicated the presence of three sp3 carbon chains
(
a: -CH
c: -CH
lished by HMBC analysis as follows. The HMBC cross-
2
CH
2
CH
2
CH-; b: -CH
2 2 3 2
CHCH CH(CH )CH -;
2
CH
2
CH
2
-). The gross structure of 1 was estab-
6
241-6245. (l) Morita, H.; Kobayashi, J. J. Org. Chem. 2002, 67, 5378-
5381.
J. Org. Chem, Vol. 70, No. 2, 2005 659

Katakawa et al.
SCHEME 1a
a
Reagents and conditions: (a) Ac2O, pyridine, 100 °C, 98%. (b) 10% HCl, reflux, 84%. (c) NaH, HMPA, THF, rt then CS2, MeI, rt, 47%
n
(
with 49% recovery of 4). (d) Bu3SnH, AIBN, toluene, reflux, 77%. (e) MeOTf, MeCN, rt. (f) Zn, AcOH, rt, 99% (in two steps). (g) NH2OH‚HCl,
AcONa, EtOH, reflux, 80%. (h) NaOH, MeOH, reflux, 52%.
structure and the absolute configuration of which has
been proven by X-ray analysis.10g To complete the trans-
formation, the removal of a hydroxyl group at C-8, the
to the reductive ring-opening reaction developed above.
Conversion of 11 to a quaternary ammonium intermedi-
ate and subsequent treatment with Zn powder in AcOH
afforded two C-4 epimeric compounds 12 and 13 in 34%
and 30% yields, respectively. 12 showed the desired (R)
configuration on C-4 (H-4â) by X-ray crystallographic
analysis. On the other hand, 13 could be epimerized at
4
ring opening at the N-C bond, the oxidation of the
secondary hydroxyl group at C-13, and the regioselective
oximation at C-5 were required. Along this line, two
strategies have been assayed as described below.
Initially, according to the procedure reported in the
t
t
C-4 under basic conditions ( BuOK in BuOH, 12:13 )
1:1), enabling the convergence of 13 into 12. The oxima-
tion of diketone 12 with 1 equiv of hydroxylamine
hydrochloride under conventional conditions (AcONa,
EtOH, reflux) gave the undesired regioisomer 14. From
the Dreiding-model analysis, we anticipated that when
12 was treated with diethylamine, only the carbonyl
function at C-5 would be condensed with the dialkyl-
amine to produce iminium salt 15. In contrast, the
carbonyl group at C-13 in 12 would be intact under these
conditions because of the severe steric repulsion between
the alkyl group on a quaternary nitrogen atom at C-13
and the alkyl chain at C-12 in spurious iminium inter-
mediate 16. Therefore, in possible intermediate 15,
hydroxylamine would condense with the more reactive
iminium function at C-5 to yield the desired oximation
product. On the basis of this idea, 12 was actually treated
with excess diethylamine in EtOH, followed by the
addition of hydroxylamine hydrochloride to give mono-
oxime compounds (1 and 17) in 46% and 19% yields,
respectively. The major product was identical with
1
0c
literature, monoacetate (4) was prepared from serra-
tinine (3), which has been previously isolated from
Lycopodium serratum Thunb. var. Thunbergii Makino
(
Japanese name Hosoba-Tohogeshiba).10a Then, the free
secondary hydroxyl group in 4 was removed by Barton’s
1
1
procedure. Xanthate derivative 5 was exposed to the
radical condition by using n-Bu SnH in the presence of
AIBN to afford deoxy derivative 6. Initial attempts at the
reductive bond cleavage between C -N in 6 by applying
O or Zn/AcOH) gave the
3
4
known procedures1
0c,h
(Zn/Ac
2
ring-opening product in poor yield. Then, we developed
an alternative condition that involved the reductive bond
cleavage of an R-ammonium carbonyl function. Quater-
nary ammonium derivative 7, which was prepared by
using MeOTf in CH
AcOH at room temperature to give ring-opening product
in high yield. The structure was established by X-ray
2 2
Cl , was treated with Zn powder in
8
crystallographic analysis, revealing that the stereochem-
istry at C-4 was S. However, the synthetic route via
intermediate 8 met with failure. The epimerization at C-4
in 8 did not occur under basic condition, probably because
1
13
natural lycoposerramine-B ( H, C NMR, IR, low- and
high-resolution MS, and CD spectra).
8
would be more thermodynamically stable than its C-4
epimer as described by Heathcock in their synthetic study
The spectroscopic data of minor product 17 were almost
superimposable with those of 1 except for the chemical
shift of some protons and carbons. The structures inferred
by extensive 2D-NMR analyses including NOESY experi-
ments indicated that both compounds were geometrical
isomers on the oxime function. The E/Z geometry of the
oxime function in 1 and 17 was estimated by comparing
the chemical shifts of the protons12 and carbons at C-4
and C-6. As shown in Table 2, the proton signal at C-4
8
on fawcettimine (2). In addition the conversion of the
hydroxyl group at C-13 into the ketone failed in 10 that
had a labile oxime function under the attempted oxida-
tion conditions.
Therefore, we adopted an alternative strategy that
featured regioselective oximation (Scheme 2). Initially,
13
diketone derivative 111 prepared from 6 was subjected
0h
(
11) (a) Barton, D. H. R.; McCombie, S. W. J. Chem. Soc., Perkin
Trans. 1 1975, 1574-1585. (b) Durand-Reville, T.; Gobbi, L. B.; Gray,
B. L.; Ley, S. V.; Scott, J. S. Org. Lett. 2002, 4, 3847-3850.
(12) Denmark, S. E.; Dappen, M. S. J. Org. Chem. 1984, 49, 798-
806.
660 J. Org. Chem., Vol. 70, No. 2, 2005

Synthesis of Lycoposerramine-B
SCHEME 2a
a
Reagents and conditions: (a) KOH, MeOH, reflux, quant. (b) Jones reagent, acetone, rt, 98%. (c) MeOTf, MeCN, rt. (d) Zn, AcOH, rt;
t
t
1
1
2, 34%; 13, 30%. (e) BuOK, BuOH, rt; 12, 30%; 13, 32%. (f) NH2OH‚HCl, AcONa, EtOH, reflux, 70%. (g) Et2NH, EtOH then NH2OH‚HCl;
, 46%; 17, 19%.
SCHEME 3. Hypothetical Biogenetic Route from Fawcettimine (2) to Lycoposerramine-B (1) and Related
Alkaloids
TABLE 2. 1H and 13C Chemical Shift at C-4 and C-6 of 1
and 17 in CDCl3
at higher field and, on the contrary, that of C-4 was
observed downfield from the corresponding signals of 17.
Consequently, the geometry of the oxime function of 1
was E and that of 17 was Z. We conclude that the
structure of lycoposerramine-B, including the oxime
geometry as well as the absolute configuration, corre-
sponds to formula 1.
position
1
17
H-4
3.18 (1H, d-like, 2.8)
3.59 (1H, br s)
2.12 (1H, m)
2.40 (1H, m)
39.6
H-6a
H-6b
C-4
2.20 (1H, m)
2.54 (1H, ddd, 1.1, 9.5, 19.0)
42.9
28.7
C-6
31.3
3
. Hypothetical Biogenetic Route from Fawcett-
imine. The hypothetical biogenetic route of 1 and other
related alkaloids starting from fawcettimine (2) was
proposed as follows (Scheme 3). Two diketo compounds
of 1 (δ 3.18) was observed at a higher field than that of
7 (δ 3.59), whereas the signals at C-6 of 1 (δ 2.20, 2.54)
were observed at a lower field than that of 17 (δ 2.12,
.40) . In addition, the signal due to C-6 of 1 was observed
1
1
2 and 13, which were obtained in the present synthetic
2
work, would be biogenetic precursors for lycoposer-
4
5
ramines-A, -B (1), and -S. The carbonyl group at C-5 in
12 would be converted into the oxime function to afford
(13) Levy, G. C.; Nelson, G. L. J. Am. Chem. Soc., 1972, 94, 4897-
4
901.
J. Org. Chem, Vol. 70, No. 2, 2005 661

Katakawa et al.
lycoposerramine-B (1). On the other hand, lycoposer-
ramines-A and -S would be produced from 13 via several
metabolic processes including amination, reduction, and
cyclization.
added MeOTf (21.0 µL, 0.186 mmol) under argon atmosphere.
After removal from the ice bath, the reaction mixture was
stirred at room temperature for 4.5 h. The solvent was removed
under reduced pressure and the residue was subjected to the
1
next reaction without purification. H NMR (400 MHz, CDCl
3
)
δ 4.69 (1H, br s), 3.26 (3H, s), 1.94 (3H, s), 0.94 (3H, d, J ) 6.2
Experimental Section
+
Hz); FAB-MS (NBA) m/z 320 [M] .
Lycoposerramine-B (1). Colorless amorphous powder; CD
Reductive Ring Opening Reaction of 7. The crude
quaternary salt prepared above was dissolved in AcOH (2.0
mL) at room temperature. Then zinc powder (744.5 mg) was
added and the reaction mixture was stirred vigorously. After
the solution was stirred for 14.5 h, the zinc powder was filtered
(
0.90 mM, MeOH, 24 °C) (∆ꢀ) 331 (0), 298 (+3.2), 237 (-0.1),
2
08 nm (+2.6); IR (CHCl
3
) νmax 3279 (hydroxyl group), 1699
-
1
1
13
(
ketone) cm ; H and C NMR data, see Table 1; EI-MS (%)
+
m/z 292 ([M] , 21.0), 275 (35.2), 202 (100); HR-FAB-MS (NBA/
PEG) m/z 293.2227 (M + H, calcd for C17
29 2 2
H N O 293.2229).
1
0c
off, and the filtrate was basified with NaHCO
with CHCl . The combined organic phase was washed with
brine, dried over MgSO , and evaporated. The residue was
purified over SiO gel (100% AcOEt) to afford 8 (53.2 mg, 99%)
as colorless prisms; mp 123-124 °C (recrystallized from
3
and extracted
Deoxygenation of 4. To a stirred solution of 4 (157.0
3
mg, 0.489 mmol) in dry THF (3.0 mL) were added dry HMPA
4
(
170 µL, 0.977 mmol) and NaH (60%, 42.4 mg, 1.06 mmol) at
2
room temperature under argon atmosphere. After the solution
was stirred for 30 min, CS (120 µL, 1.99 mmol) was added
2
2
4
AcOEt); [R]
and ketone) cm ; H NMR (500 MHz, CDCl
s, H-13), 2.81 (1H, br s, H-4), 2.51 (1H, m, H-9), 2.31 (3H, m,
D
+92.4 (c 0.42, CHCl
3
); IR (KBr) νmax 1738 (ester
and the solution was stirred for an additional 4 h at room
temperature. Then MeI (97.0 µL, 1.56 mmol) was added and
the reaction mixture was stirred for 3.5 h at the same
temperature. The reaction mixture was poured into ice-cold
-
1 1
3
) δ 4.96 (1H, br
3
H-1, 1, 9), 2.25 (3H, s, N-CH ), 2.25 (2H, m, H-6, 6), 2.15 (1H,
m, H-7), 1.88 (3H, s, -OAc), 1.85 (1H, m, H-3), 1.77 (1H, m,
water and extracted with CHCl
was washed with brine, dried over MgSO
The residue was chromatographed over SiO
CHCl then MeOH) to give xanthate 5 (94.5 mg, 47%) as a
colorless amorphous powder: [R]
CHCl ) νmax 1739 (ester, ketone) cm ; H NMR (400 MHz,
CDCl ) δ 5.77 (1H, br s), 4.75 (1H, br s), 3.54 (1H, dd, J )
0.8, 10.8 Hz), 2.83 (1H, ddd, J ) 9.3, 9.3, 12.5 Hz), 2.74 (1H,
3
. The combined organic layer
, and evaporated.
gel (15% n-hex/
H-15), 1.71 (3H, m, H-11, -11, -14), 1.63 (1H, m, H-8), 1.60
4
(
(
1H, m, H-2), 1.58 (1H, m, H-10), 1.40 (2H, m, H-8, -10), 1.32
2
1H, m, H-2), 1.31 (2H, m, H-3, 14), 0.91 (3H, d, J ) 6.4 Hz,
3
1
3
2
2
H-16); C NMR (125 MHz, CDCl ) δ 218.5 (C-5), 169.8 (OAc),
-38.1 (c 1.37, CHCl
3
); IR
3
D
-
1
1
74.9 (C-13), 58.9 (C-1), 57.0 (C-4), 55.9 (C-9), 46.8 (C-12), 45.7
(
3
3
(N-CH ), 39.7 (C-6), 37.5 (C-7), 34.2 (C-14), 32.6 (C-11), 32.1
3
1
(C-8), 26.7 (C-2), 22.4 (C-10), 21.9 (C-3 and -16), 21.0 (-OAc),
+
dd, J ) 10.6, 18.7 Hz), 2.72 (1H, m), 2.60 (3H, s), 2.57 (1H,
ddd, J ) 1.5, 8.4, 12.4 Hz), 2.25-2.17 (2H, m), 2.01-1.44 (10H,
m), 1.95 (3H, s), 1.20 (1H, ddd, J ) 4.2, 13.5, 13.5 Hz), 0.98
20.7 (C-15); EI-MS (%) m/z 321 ([M] , 61.9), 292 (25.6), 278
(18.4), 262 (33.4), 249 (14.0), 232 (8.6), 219 (10.1), 206 (100),
189 (22.9), 178 (8.3); HR-FAB-MS (NBA/PEG) m/z 322.2358
1
3
(
1
2
(
(
3H, d, J ) 7.0 Hz); C NMR (100 MHz, CDCl
3
) δ 215.3, 211.8,
69.5, 83.6, 77.1, 76.0, 52.2, 50.1, 43.5, 36.4, 35.7, 29.3, 26.8,
4.4, 21.11, 21.08, 20.9, 20.4, 19.1, 16.9; EI-MS (%) m/z 411
3
(M + H, calcd for C19H32NO 322.2382).
Oxime Formation of 8. To a stirred solution of 8 (21.2
mg, 0.0660 mmol) in dry EtOH (1.0 mL) were added NH OH‚
HCl (18.4 mg, 0.265 mmol), AcONa (35.1 mg, 0.428 mmol),
and H O (55 µL) at room temperature under argon atmo-
sphere. After refluxing for 11.5 h, the mixture was cooled,
poured into chilled NaHCO solution, and extracted with 5%
MeOH/CHCl . The combined organic phase was washed with
brine, dried over MgSO , and evaporated. The residue was
chromatographed over silica gel (0-8% MeOH/CHCl ) to afford
(17.7 mg, 80%) as a colorless amorphous powder; [R]
c 0.96, CHCl ); IR (CHCl ) νmax 3292 (hydroxyl group), 1727
ester) cm ; H NMR (400 MHz, CDCl ) δ 4.99 (1H, br s), 3.19
1H, br s), 2.47-2.65 (3H, m), 2.27-2.45 (3H, m), 2.27 (3H, s),
2
+
[M] , 4.7), 383 (49.4), 368 (40.0), 324 (93.7), 292 (32.3), 276
100), 256 (53.1), 216 (51.6), 194 (70.5), 152 (82.3); HR-FAB-
2
MS (NBA/PEG) m/z 412.1642 (M + H, calcd for C20
H
30NO
4
S
2
4
SiO
12.1616). The MeOH eluate was rechromatographed over
3
2
gel (2% MeOH/AcOEt) to recover 4 (76.9 mg, 49%).
3
To a solution of the xanthate 5 (249.8 mg, 0.608 mmol) in
SnH (330 µL, 1.23
4
dry toluene (8.0 mL) were added n-Bu
3
3
mmol) and AIBN (29.7 mg, 0.181 mmol) at room temperature
under argon atmosphere. After being stirred under reflux for
22
9
D
+0.8
(
(
(
3
3
1
h, the reaction mixture was cooled and extracted with 5%
HCl aq. The aqueous layer was basified with NaHCO and
extracted with CHCl . The combined organic layer was washed
with brine, dried over MgSO , and evaporated. The residue
gel (100% CHCl ) to give 6 (131.7 mg,
-1 1
3
3
3
13
1
.91 (3H, s), 1.20-2.00 (15H, m), 0.89 (3H, d, J ) 6.7 Hz); C
4
3
NMR (125 MHz, CDCl ) δ 170.7, 170.1, 74.7, 58.9, 55.6, 48.1,
was purified over SiO
2
3
4
2
7.3, 45.8, 39.0, 34.6, 32.2, 32.1, 30.7, 26.2, 24.3, 22.1, 22.0,
1.2, 20.7; EI-MS (%) m/z 336 ([M] , 10.5), 320 (97.6), 319
7
7%) as colorless prisms; mp 198-200°C (recrystallized from
+
2
4
n-hex/CHCl
3
); [R]
D
-11.0 (c 0.94, CHCl
3
); IR (KBr) νmax 1739
(
100), 277 (14.6), 259 (26.3), 242 (16.6), 221 (20.6), 216 (18.3),
-
1
1
(
(
ketone and ester) cm ; H NMR (500 MHz, CDCl ) δ 4.66
3
2
04 (21.7), 186 (27.4); HR-FAB-MS (NBA/PEG) m/z 337.2460
M + H, calcd for C19 337.2491).
Deacetylation of 9. Oxime derivative 9 (7.5 mg, 0.0223
1H, br s, H-13), 3.07 (1H, ddd, J ) 5.2, 10.9, 10.9 Hz, H-7),
(
33 2 3
H N O
2
.90 (1H, ddd, J ) 9.4, 9.4, 12.3 Hz, H-1), 2.73 (1H, br d, J )
0.4 Hz, H-9), 2.59 (1H, ddd, J ) 1.5, 8.2, 12.2 Hz, H-1), 2.54
1
mmol) was dissolved in 5% NaOH/MeOH solution (2.0 mL) and
refluxed for 7 h under argon atmosphere. After cooling, the
solution was poured into ice and extracted with 5% MeOH/
(
1H, dd, J ) 10.4, 18.9 Hz, H-6), 2.35 (1H, dd, J ) 11.0, 18.9
Hz, H-6), 2.24 (1H, ddd, J ) 3.1, 12.1, 12.1 Hz, H-9), 1.95 (1H,
m, H-2), 1.93 (3H, s, -OAc), 1.90 (2H, m, H-10 and -11), 1.79
CHCl
dried over MgSO
graphed over amino silica gel (0-5% MeOH/CHCl
3.4 mg, 52%) as a colorless amorphous powder; [R]
(c 0.42, CHCl ); IR (CHCl ) νmax 3315 (hydroxyl group) cm
H NMR (400 MHz, CDCl ) δ 3.92 (1H, br s), 3.27 (1H, br s),
3
. The combined organic phase was washed with brine,
, and evaporated. The residue was chromato-
) to give 10
(1H, m, H-15), 1.75 (1H, m, H-2), 1.72 (1H, m, H-14), 1.65 (1H,
m, H-8), 1.61 (1H, m, H-3), 1.55 (1H, m, H-10), 1.48 (1H, ddd,
J ) 4.9, 10.1, 13.1 Hz, H-3), 1.35 (1H, ddd, J ) 5.5, 12.5, 14.0
Hz, H-8), 1.30 (1H, ddd, J ) 2.1, 12.5, 14.6 Hz, H-14), 1.13
4
3
2
3
(
D
+24.0
-
1
1H, ddd, J ) 4.7, 14.0, 14.0 Hz, H-11), 0.91 (3H, d, J ) 6.4
3
3
;
1
3
1
Hz, H-16); C NMR (125 MHz, CDCl
3
3
2.65 (1H, ddd, J ) 1.5, 12.1, 18.1 Hz), 2.59 (1H, m), 2.49 (1H,
dd, J ) 9.5, 18.1 Hz), 2.29 (3H, s), 2.20-2.45 (3H, m), 1.80-
2.10 (4H, m), 1.20-1.75 (12H, m), 0.91 (3H, d, J ) 6.4 Hz);
1
2
1
2), 38.2 (C-6), 34.1 (C-14), 32.4 (C-7), 31.9 (C-8), 24.8 (C-11),
1.9 (C-16), 21.4 (C-3**), 21.2 (C-2**), 21.1 (OAc**), 20.6 (C-
1
3
0***), 20.5 (C-15***) [*, **, *** are interchangeable]; EI-MS
3
C NMR (125 MHz, CDCl ) δ 171.8, 73.2, 58.9, 55.9, 47.9, 47.8,
+
(
%) m/z 305 (M , 12.3), 291 (42.4), 277 (100), 232 (99.9), 219
82.9), 218 (95.6), 194 (99.1), 176 (29.3), 152 (94.4), 150 (97.7).
Preparation of Quaternary Salt (7). To an ice-cooled
46.1, 38.8, 38.0, 32.5, 32.3, 31.1, 26.3, 24.6, 22.6, 22.2, 20.0;
+
(
EI-MS (%) m/z 294 ([M] , 16.0), 278 (100), 277 (99.3), 260
(66.7), 234 (27.8), 220 (58.8), 204 (54.3); HR-FAB-MS (NBA/
solution of 6 (50.9 mg, 0.167 mmol) in dry MeCN (1.5 mL) was
31 2 2
PEG) m/z 295.2364 (M + H, calcd for C17H N O 295.2386).
662 J. Org. Chem., Vol. 70, No. 2, 2005

Synthesis of Lycoposerramine-B
Preparation of 12 and 13. 12 and 13 were obtained from
1.58 (1H, m, H-8), 1.42 (3H, m, H-2, -10, -14), 1.28 (2H, m,
1
3
1
1 (25.1 mg, 0.0954 mmol) as a mixture, using the same
H-3, -10), 1.02 (3H, d, J ) 6.4 Hz, H
CDCl ) δ 221.5 (C-5), 161.2 (C-13), 55.1 (C-9), 52.7 (C-12), 51.6
(C-4), 48.3 (C-1), 44.3 (N-CH
3
-16); C NMR (125 MHz,
procedure as that described above. The mixture was purified
over SiO
3
2
gel (0-4% MeOH/CHCl
3
) to afford 12 (9.1 mg, 34%)
3
), 40.8 (C-7), 38.5 (C-6), 31.3 (C-
as colorless prisms and 13 (7.9 mg, 30%) as a colorless
amorphous powder.
8), 28.5 (C-14), 28.0 (C-2), 27.2 (C-15), 24.4 (C-11), 22.4 (C-3),
22.3 (C-16), 21.4 (C-10); FAB-MS (NBA) m/z 293 (M + H); HR-
Spectroscopic data for 12: mp 112-113°C (crystallized from
29 2 2
FAB-MS (NBA/PEG) m/z 293.2203 (M + H, calcd for C17H N O
2
3
n-hexane); [R]
D
+191 (c 0.49, CHCl
3
); IR (KBr) νmax 1739,
) δ 2.89 (1H,
d-like, J ) 5.2 Hz), 1.20-2.60 (20H, overlap), 2.26 (3H, s,
293.2229).
-
1
1
1
700 (ketone) cm ; H NMR (400 MHz, CDCl
3
Preparation of Lycoposerramine-B (1) from 12. To a
solution of 12 (7.6 mg, 0.0274 mmol) in dry EtOH (0.5 mL)
was added diethylamine (13.0 µL, 0.126 mmol) at room
temperature under argon atmosphere. After the mixture was
stirred for 3 h at room temperature, a solution of hydroxy-
lamine hydrochloride (2.1 mg, 0.0302 mmol) in EtOH (84 µL)
was added to the reaction mixture, and then it was stirred for
15 h at room temperature. The reaction mixture was basified
with chilled sat. NaHCO3 solution and extracted with 5%
1
3
N-CH
CDCl
9.4, 31.1, 30.2, 28.0, 25.3, 22.5, 22.3, 21.6; FAB-MS (NBA)
m/z 278 (M + H); HR-FAB-MS (NBA/PEG) m/z 278.2100 (M
H, calcd for C17 278.2120).
Spectroscopic data for 13: [R]
) νmax 1736, 1699 (ketone) cm ; H NMR (400 MHz,
) δ 1.25-2.55 (21H, overlap), 2.25 (3H, s, N-CH ), 1.06
) δ 216.2,
3
), 1.07 (3H, d, J ) 6.4 Hz, H
3
-16); C NMR (125 MHz,
3
) δ 220.2, 214.2, 60.6, 54.7, 50.2, 48.7, 46.6, 44.2, 42.5,
3
+
H28NO
2
2
2
D
3
+123 (c 0.43, CHCl ); IR
1 1
-
(
CHCl
3
CDCl
3
3
MeOH/CHCl . The combined organic phase was washed with
3
13
(
2
3
3H, d, J ) 6.0 Hz, H
3
-16); C NMR (125 MHz, CDCl
3
brine, dried over MgSO , and evaporated. The residue was
4
14.8, 60.5, 58.1, 57.1, 55.0, 46.9, 45.7, 42.1, 38.5, 31.5, 31.2,
chromatographed over SiO2 gel (0-20% MeOH/CHCl ) to
3
0.6, 27.1, 23.3, 22.21, 22.17; FAB-MS (NBA) m/z 278 (M +
afford crude 1 and pure 17 (1.5 mg, 19%). Crude 1 (12-18%
H); HR-FAB-MS (NBA/PEG) m/z 278.2100 (M + H, calcd for
MeOH/CHCl eluate) was rechromatographed over amino
3
C
17
H
28NO
2
278.2120).
silica gel (0-50% AcOEt/n-hex) to afford 1 (3.7 mg, 46%) as a
colorless amorphous powder. The spectroscopic data (IR, CD,
NMR, and MS) for 1 were completely identical with those of
natural lycoposerramine-B.
Epimerization of 13 for Conversion into 12. To a stirred
t
solution of 13 (11.4 mg, 0.0412 mmol) in dry BuOH (0.8 mL)
t
was added BuOK (2.6 mg, 0.0231 mmol) at room temperature
under argon atmosphere. After being stirred for 3 h at room
temperature, the reaction mixture was poured into water and
Spectroscopic data for 17: colorless solid; CD (0.27 mM,
MeOH, 25 °C) (∆ꢀ) 336 (0), 298 (+16.2), 243 (+0.9), 206 nm
extracted with 5% MeOH/CHCl
was washed with brine, dried over MgSO
The residue was chromatographed on SiO
CHCl ) to afford 12 (3.4 mg, 30%) and recovered 13 (3.6 mg,
2%).
Preparation of 14. To a solution of 12 (1.5 mg, 0.00542
3
. The combined organic phase
, and evaporated.
gel (0-5% MeOH/
(
+18.9); IR (CHCl
3
) νmax 3292 (hydroxyl group), 1699 (ketone)
) δ 3.59 (1H, br s, H-4), 2.71
-1 1
4
cm ; H NMR (600 MHz, CDCl
3
2
(
1H, br, H-1), 2.40 (1H, m, H-6), 2.39 (1H, m, H-7), 2.30 (2H,
3
m, H
2
-9), 2.28 (1H, m, H-14), 2.28 (3H, br s, N-CH
3
), 2.24 (1H,
3
m, H-11), 2.22 (1H, m, H-14), 2.12 (1H, m, H-6), 2.10 (1H, m,
H-15), 2.00 (2H, m, H-1, -11), 1.92 (1H, m, H-3), 1.74 (2H, m,
mmol) in dry EtOH (0.2 mL) were added an aqueous solution
containing hydroxylamine hydrochloride (0.42 mg, 0.00607
mmol) and AcONa (0.82 mg, 0.00996 mmol) at room temper-
ature under argon atmosphere. The reaction mixture was
refluxed for 6 h and then cooled to room temperature. The
H
2
-8), 1.67 (1H, br, H-2), 1.62 (1H, br, H-2), 1.37 (1H, br, H-10),
1
.25 (1H, m, H-3), 1.17 (1H, m, H-10), 1.04 (3H, d, J ) 6.3 Hz,
13
H-16); C NMR (125 MHz, CDCl
3
) δ 214.0 (C-13), 169.0 (C-
), 61.8 (C-12), 55.0 (C-9), 48.3 (C-1), 46.6 (C-14), 44.2 (N-CH ),
3.2 (C-7), 39.6 (C-4), 31.3 (C-6), 31.2 (C-8), 30.0 (C-15), 27.9
5
4
(
3
reaction mixture was basified with chilled sat. NaHCO
solution and extracted with 5% MeOH/CHCl . The combined
organic phase was washed with brine, dried over MgSO , and
evaporated. The residue was chromatographed over SiO gel
0-20% MeOH/CHCl ) to afford 14 (1.1 mg, 70%) as a colorless
amorphous powder; CD (0.48 mM, MeOH, 25 °C) (∆ꢀ) 328 (0),
3
C-2), 24.8 (C-11), 24.0 (C-3), 22.4 (C-16), 21.2 (C-10); FAB-
MS (NBA) m/z 293 (M + H); HR-FAB-MS (NBA/PEG) m/z
15.2039 (M + Na, calcd for C17 Na 315.2048).
3
4
3
28 2 2
H N O
2
(
3
Supporting Information Available: General experimen-
1
13
1
1
tal procedure, NMR spectra ( H NMR, C NMR, H- H COSY,
2
(
95 (+6.1), 243 (0), 210 nm (+10.0); IR (CHCl
3
) νmax 3339
H NMR (500 MHz,
3
) δ 3.29 (1H, ddd, J ) 13.4, 4.1, 1.4 Hz, H-14), 2.84 (1H,
1
HMQC, HMBC and J-resolved HMBC) of 1, NMR spectra ( H
and C) of 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, and 17, X-ray
-
1
1
hydroxyl group), 1730 (ketone) cm
;
13
CDCl
crystallographic data of 8 and 12, and comparison of NMR
spectra of natural and synthetic 1. This material is available
free of charge via the Internet at http://pubs.acs.org.
br s, H-4), 2.64 (1H, dd, J ) 13.0, 13.0 Hz, H-1), 2.40 (1H, m,
H-7), 2.35 (2H, m, H
8.9, 19.2 Hz, H-6), 2.05 (3H, m, H-1, -11, -11), 2.04 (1H, m,
H-6), 1.98 (1H, m, H-3), 1.79 (1H, m, H-15), 1.75 (1H, m, H-2),
2 3
-9), 2.28 (3H, s, N-CH ), 2.20 (1H, dd, J
)
JO0483825
J. Org. Chem, Vol. 70, No. 2, 2005 663