Total synthesis of stevastelins: Structure confirmation of stevastelins B and B3, and structure revision of stevastelin C3

Article abstract of DOI:10.1246/bcsj.79.921

The total syntheses of stevastelins B, B3, C3, and the 5-deoxy derivative of stevastelin C3, novel cyclic depsipeptides starting from L-quebrachitol, and amino acids are described. Stereoselective introduction of two methyl groups into L-quebrachitol, followed by regioselective cleavage of the cyclohexane ring by way of the Baeyer-Villiger reaction effectively afforded the fatty acid moiety of stevastelins. Introduction of the peptide and subsequent macrolactamization gave stevastelin B. Stevastelins C3 and B3 were also synthesized by a similar way. The direct comparison of synthetic stevastelins with natural compounds revealed that the synthetic stevastelins B and B3 are identical to the natural products, confirming the proposed structures. However, the synthetic stevastelin C3 was found to not be identical with the natural product. To elucidate the structure of stevastelin C3, degradation of the natural product was carried out to show the possibility that the natural product could be a 5-deoxy derivative of the proposed structure. Thus, the 5-deoxy derivative of the fatty acid moiety was prepared and transformed into a macrocycle. The synthetic 5-deoxy compound was fully identical to natural stevastelin C3. Based on these studies, it was shown that the structure of stevastelin C3 should be revised.

Full text of DOI:10.1246/bcsj.79.921

ꢀ 2006 The Chemical Society of Japan
Bull. Chem. Soc. Jpn. Vol. 79, No. 6, 921–937 (2006)
921
Total Synthesis of Stevastelins: Structure Confirmation of Stevastelins B
and B3, and Structure Revision of Stevastelin C3
ꢀ
Kazuo Kurosawa, Keigo Matsuura, Toshihiko Nagase, and Noritaka Chida
Department of Applied Chemistry, Faculty of Science and Technology, Keio University,
3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522
Received December 26, 2005; E-mail: chida@applc.keio.ac.jp
The total syntheses of stevastelins B, B3, C3, and the 5-deoxy derivative of stevastelin C3, novel cyclic depsipep-
tides starting from L-quebrachitol, and amino acids are described. Stereoselective introduction of two methyl groups into
L-quebrachitol, followed by regioselective cleavage of the cyclohexane ring by way of the Baeyer–Villiger reaction
effectively afforded the fatty acid moiety of stevastelins. Introduction of the peptide and subsequent macrolactamization
gave stevastelin B. Stevastelins C3 and B3 were also synthesized by a similar way. The direct comparison of synthetic
stevastelins with natural compounds revealed that the synthetic stevastelins B and B3 are identical to the natural prod-
ucts, confirming the proposed structures. However, the synthetic stevastelin C3 was found to not be identical with the
natural product. To elucidate the structure of stevastelin C3, degradation of the natural product was carried out to show
the possibility that the natural product could be a 5-deoxy derivative of the proposed structure. Thus, the 5-deoxy de-
rivative of the fatty acid moiety was prepared and transformed into a macrocycle. The synthetic 5-deoxy compound was
fully identical to natural stevastelin C3. Based on these studies, it was shown that the structure of stevastelin C3 should
be revised.
Stevastelins A, B (1), B3 (2), and C3 (3) are novel cyclic
depsipeptides that were isolated from a culture broth of
Penicilium sp. NK374186 by Nippon Kayaku group in 1994
(Fig. 1).1,2 It has been reported that stevastelins show potent
immunosuppressive activity by way of blocking human T cell
activation without affecting the phosphatase activity of calci-
neurin. With such a novel mode of action, which is different
from that of the well-known immunosuppressants FK506 and
cyclosporin A, stevastelins are expected to be new immuno-
suppressants as well as useful biochemical probes. The struc-
tural study by spectral, degradation, and synthetic methods of
stevastelin B (1), the most abundant congener of the stevastelin
family, established that stevastelin B consists of (2S,3S,4S,5R)-
3,5-dihydroxy-2,4-dimethyloctadecanoic acid, O-acetyl-L-
serine, L-threonine, and L-valine, and possesses a 15-membered
ring structure.3 Based on spectroscopic analyses of other ste-
vastelins, it has been proposed that stevastelin B3 (2) is an iso-
mer of stevastelin B (1) with a 13-membered ring structure,
and stevastelin C3 (3) is a de-O-acetyl derivative of stevastelin
B3.1 Their interesting and important mode of action as well as
unique structures have attracted synthetic attention, and the
total synthesis of stevastelin B4 and the proposed structure of
C35 have been reported. The synthetic approach to stevastelin
B,6 and preparation and biological assessment of simple ana-
logues of stevastelins have also appeared.7 Yamamoto’s group
reported the first total synthesis of 1, in which they constructed
the 15-membered macrocycle by lactamization between a car-
boxylic acid at the C-1 and an amino group in valine, and the
fatty acid moiety with four contiguous chiral centers was pre-
pared by the combination of Evans asymmetric aldol reaction
and Roush asymmetric crotylation starting from tetradecanal.4
Sarabia’s total synthesis of the proposed structure of stevaste-
lin C3 (3) employed Yamaguchi’s macrolactonization between
a hydroxy group at C-3 and a carboxylic acid in serine to con-
struct the 13-membered ring, and the fatty acid was synthe-
sized from tetradecanal by way of Evans asymmetric synthesis
methodology and an aldol reaction with a thioester.5 Recently,
Sarabia’s group has completed the total synthesis of stevaste-
lins B and B3,8 in which they utilized a base-induced translac-
tonization of a 15-membered macrocycle (stevastelin B pre-
cursor) prepared by macrolactamization between a carboxylic
acid at C-1 and an amino group in valine, to a 13-membered
one (stevastelin B3 precursor). The Sarabia’s group also re-
ported the structure–activity relationship study of stevastelin
5
3
1
n-C13H27
O
O
n-C13H27
O
5
3
1 O
4
2
4
2
O
OH HN
O
OH HN
O
O
H
N
thr
H
H
H
val
AcO
AcO
N
N
H
N
H
O
ser
O
OH
OSO3H
stevastelin A
stevastelin B (1)
n-C13H27
O
n-C13H27
O
5
3
5
3
HO
O
O
O
HN
O
HN
HO
RO
NH HN
O
NH HN
O
H
H
O
OH
O
OH
R = Ac : stevastelin B3 (2)
R = H : stevastelin C3 (3) (proposed)
stevastelin C3 (4) (revised)
Fig. 1. Structures of stevastelins.
Published on the web June 6, 2006; doi:10.1246/bcsj.79.921

922 Bull. Chem. Soc. Jpn. Vol. 79, No. 6 (2006)
Total Synthesis of Stevastelins
1
2 and 3
n-C13H27
5
3
2
5
n-C13H27
O
3
4
4
CO2H
2
CO2H
NH2
BzlO
BzlO
O
O
O
OH
H2N
O
H
H
BzlO
N
HO2C
HO
O
NH2
NHHN
N
H
H
H
O
OH
N
H
O
N
O
OH
H
O
OH
5
6
Val-Thr-Ser
+
n-C13H27
5
OH
1
3
4
2
OH OH
7
OMe
OMe
OH
OMe
HO
HO
OP
O
O
O
O
O
OH
OH
OMe
O
O
O
8
9
10
L-quebrachitol (11)
Fig. 2. Retrosynthetic analysis of stevastelins. Bzl = –CH2Ph.
B analogues.8b Chakraborty has reported the formal synthesis
of stevastelin B3 starting from methyl (S)-3-hydroxy-2-meth-
ylpropionate.9 These successful syntheses, however, did not
describe the identity of their synthetic compounds with the nat-
ural products, providing insufficient information for structure
confirmation of the natural products. In this paper, we report
a total synthesis of stevastelins B (1), B3 (2), C3 (3), and 5-
deoxy derivative of stevastelin C3 (4), which resulted in the
unambiguous confirmation of the proposed absolute structures
of stevastelins B (1) and B3 (2), and the structure revision of
stevastelin C3 to 4 in detail.10
ing blocks for total syntheses of a variety of natural products.13
Preparation of Common Fatty Acid Precursor 7. The
cyclitol derivative 13,14 prepared stereoselectively from L-que-
brachitol (11) in the known 3 steps with slight modification,
was used as the starting material for the preparation of the fatty
acid precursor 7. Tebbe olefination15 of the known ketone
1216 afforded the exo-methylene compound 13 in 64% yield
(Scheme 1). Selective removal of the trans-O-isopropylidene
group in 13 gave 14, whose hydrogenation afforded the diol
15 stereoselectively in 76% yield from 13. Removal of the iso-
propylidene group in 13 prior to hydrogenation was required
since hydrogenation of 13 was found to proceed very slowly
giving the desired product in poor yield. Reaction of 15 with
Bu2SnO17 followed by treatment with TsCl afforded 16
(82% yield), whose treatment with base cleanly provided the
ꢀ-epoxide 17 in 93% yield. Reaction of 17 with Me3Al gave
the trans-diaxial ring opening product 18 in 93% yield. The
Results and Discussion
Synthetic Plan of Stevastelins. Our retrosynthetic analysis
(Fig. 2) suggested that stevastelin B (1), possessing a 15-mem-
bered ring structure, would be obtained by macrolactamization
of the amino carboxylic acid 5, followed by deprotection and
acetylation. Stevastelins B3 (2) and C3 (3), with 13-membered
macrocycles, were also expected to derive from another amino
carboxylic acid, 6. The key intermediates 5 and 6 were
envisioned to be synthesized by condensation of a tripeptide
(Val–Thr–Ser) moiety with the fatty acid precursor 7. The tri-
peptide could be prepared from commercially available pro-
tected serine, threonine, and valine derivatives. The common
precursor 7, in turn, was planned to be constructed by carbon
elongation of the chiral epoxide 8 with a dodecyl group. The
epoxide 8 was envisioned to be synthesized by a ring cleav-
age of the 7-membered lactone 9, which would derive from
regioselective Baeyer–Villiger reaction11 of the ketone 10.
For preparation of the cyclohexanone 10, L-quebrachitol (11)
was chosen as the starting material. L-Quebrachitol (11) is a
naturally occurring optically active cyclitol, obtained in large
quantities from the serum of the rubber tree12 and has been uti-
lized as a raw material in the preparation of useful chiral build-
1
structure of 18 was confirmed by the H NMR analysis (cou-
pling constants and NOE experiments) of the derived benzoate
19 as shown in Scheme 1. PCC (pyridinium chlorochromate)
oxidation of 18 provided the ketone 10. From our earlier ob-
servations, it was highly anticipated that the Baeyer–Villiger
reaction of 10, possessing a methyl and an oxygen substitu-
ent on ꢀ- and ꢀ0-carbons, respectively, would proceed in a
highly regioselective manner.11,13 Indeed, treatment of 10 with
mCPBA afforded the expected product, the 7-membered lac-
tone 9, as the sole isomer in 81% yield from 18. Reduction
of 9 with LiAlH4 gave a triol, whose selective O-acylation af-
forded the di-O-pivalate 20 (65% yield from 9). The secondary
hydroxy group in 20 was mesylated to give 21 in 99% yield,
which was further treated with MeONa to give the inverted ep-
oxide 8 in 96% yield. Reaction of 8 with didodecylmagnesium
in the presence of CuCN18 smoothly provided 22 in 87% yield.
Deprotection of the O-methyl group in 22 by the action of tri-

K. Kurosawa et al.
Bull. Chem. Soc. Jpn. Vol. 79, No. 6 (2006)
923
OMe
OMe
OMe
OMe
O
OMe
O
OH
OH
OH
OR
X
O
O
a
c
g
d
f
O
11
O
O
O
O
OR
O
O
O
O
15 : R = H
16 : R = Ts
18 : R = H
19 : R = Bz
14
17
12 : X = O
e
h
b
i
13 : X = CH2
3%
7%
OMe
OMe
Me
H
OMe
PivOH2C
k,l
j
CH2OPiv
18
5
H
O
2
H
Me
6%
O
O
O
OR OMe
O
1
6
O
O
BzO
O
H
O
20 : R = H
m
9% NOE
10
9
21 : R = Ms
J1,2 = 3.7 Hz
J
J
1,6 = 9.2 Hz
5,6 = 7.0 Hz
n-C13H27
OH
f
OPiv
n
O
OH OR
Selected NMR data of 19
OMe
22 : R = Me
7 : R = H
8
o
Scheme 1. Ts = –SO2C6H4(p-Me), Ms = –SO2Me, Bz = –COPh, Piv = –COCMe3. Reagents and conditions: a) see Ref. 16;
b) Tebbe reagent, THF; c) p-TsOH (cat), MeOH, 0 ꢃC; d) H2, Raney-Ni, EtOH; e) Bu2SnO, MeOH, reflux, then TsCl, DMAP, 1,4-
dioxane; f) MeONa, MeOH; g) Me3Al in hexane, CH2Cl2; h) BzCl, DMAP, pyridine; i) PCC–Al2O3, CH2Cl2; j) mCPBA, KHCO3,
(CH2Cl)2; k) LiAlH4, THF; l) PivCl, DMAP, pyridine; m) MsCl, pyridine; n) (n-C12H25)2Mg, CuCN, Et2O; o) TMSI, CH2Cl2.
methylsilyl iodide19 afforded the precursor of the fatty acid
moiety 7 in 93% yield. The spectroscopic data and ½ꢀꢁD value
of 7 showed good accordance with those reported for the
authentic compound derived from the natural stevastelin B
(1) by reductive degradation.3b
cleanly separated by silica-gel chromatography to give com-
pounds 26 (58% yield from 23) and 27 (9% from 23) in pure
forms, respectively. Acid hydrolysis of 26 gave the triol 28 in
94% yield. The primary alcohol in 28 was selectively oxidiz-
ed with TEMPO25 (2,2,6,6-tetramethyl-1-piperidinyloxy, free
radical) to give aldehyde, which was further oxidized by so-
dium chlorite to afford the carboxylic acid 29. Treatment of
29 with trifluoroacetic acid (TFA) provided the amino carbox-
ylic acid 5 as its TFA salt. The crucial step, macrolactamiza-
Total Synthesis of Stevastelin B. Having established the
preparation of the common precursor 7 for the synthesis of
stevastelins, the total synthesis of stevastelin B, possessing a
15-membered cyclic depsipeptide structure, was first explored.
Treatment of 7 with 2-methoxypropene in the presence of
camphorsulfonic acid (CSA)20 afforded the kinetic acetonide
23 in 76% yield (Scheme 2). To introduce a tripeptide into
23, direct acylation of 23 with Boc–Val–Thr–Ser(Bzl) under
various reaction conditions were attempted. However, none
of the acylated product was obtained even under Yamaguchi’s
conditions.21a Recognition of the poor reactivity of the hy-
droxy group in 23, probably due to steric hindrance, led us
to employ the stepwise introduction of the peptide moiety. Al-
though condensation of 23 with Cbz–Ser(Bzl)22 under Keck
conditions23 using dicyclohexylcarbodiimide (DCC) and 4-(di-
methylamino)pyridine (DMAP) gave no desired product, un-
der Yamaguchi’s conditions21a the acylated products were suc-
cessfully afforded. Unfortunately, partial racemization of the
serine moiety during the condensation process was observed,
and compound 24 and its D-serine isomer were obtained as
an inseparable mixture in a ratio of ca. 6:1 (determined with
300 MHz 1H NMR) in 73% yield. Hydrogenolysis of a mixture
of 24 and its epimer in the presence of a 10% Pd/C ethylene-
diamine complex24 selectively deprotected the N-Cbz group to
give amines, which, without isolation, were coupled with Boc–
Val–Thr (25) by the action of 1-(3-dimethylaminopropyl)-3-
tion of 5 TFA, was successfully carried out by Shioiri’s proto-
ꢂ
col26 using diethylphosphoryl cyanide (DEPC) in DMF under
high dilution conditions (0.01 M) to provide the 15-membered
macrocycle 30 in 41% yield from 29. Removal of the O-benzyl
group in 30 by hydrogenolysis afforded the triol 31, which was
treated with acetic anhydride in pyridine at 0 ꢃC to furnish ste-
vastelin B (1) in 67% yield from 30. Direct comparison of syn-
thetic 1 with natural stevastelin B, kindly provided by Nippon
Kayaku Co., Ltd., revealed that the synthetic compound is
unambiguously identical to the natural product, therefore con-
firming the proposed whole structure of stevastelin B (1).
Synthesis of Macrocycles Possessing Proposed Struc-
tures of Stevastelins B3 and C3: Structure Confirmation
of Stevastelin B3. Successful total synthesis of stevastelin
B led us to investigate the synthesis of stevastelins B3 (2)
and C3 (3), whose 13-membered structures have not been syn-
thetically confirmed, based on a similar methodology em-
ployed for the synthesis of stevastelin B.
Synthesis of stevastelin B3 (2) commenced from the aceto-
nide 23 (Scheme 3). Benzylation of the hydroxy group in 23,
followed by acid hydrolysis gave the diol 32. The primary hy-
droxy group in 32 was selectively protected as a TES ether to
give 33 in 96% yield from 23. Although coupling of 33 with
Cbz–Ser(Bzl) was first attempted under Yamaguchi’s condi-
tions, the desired product 34 was not obtained. After several
ethylcarbodiimide hydrochloride (WSC HCl) and 1-hydroxy-
benzotriazole (HOBt) to provide a mixture of 26 and its dia-
stereomer 27 in 95% yield. At this stage, diastereomers were
ꢂ

924 Bull. Chem. Soc. Jpn. Vol. 79, No. 6 (2006)
Total Synthesis of Stevastelins
tained as an inseparable mixture in a ratio of ca. 1:1 in 77%
yield under the modified Yamaguchi’s conditions. Shiina’s
method also provided a 1:1 mixture of 34 and its epimer in
36% yield. To suppress racemization in the serine moiety,
various reaction parameters (temperature, solvent, time,
amount of reagents, and so on) were examined in the modified
Yamaguchi’s and Shiina’s conditions; however, improved
results could not be obtained. Selective deprotection of the
N-Cbz group in 34 and its diastereomer afforded amines,
which, without isolation, were coupled with the dipeptide 25
n-C13H27
O
n-C13H27
a
b
7
O
O
O
OH
O
O
BzlO
NHCbz
24 + D-serine isomer
23
n-C13H27
O
O
H
O
O
O
O
NHBoc
in the presence of WSC HCl and HOBt to provide a mixture
ꢂ
H
BzlO
N
of 35 and its diastereomer in 94% yield. Removal of the O-
TES group, followed by chromatographic separation gave dia-
stereomerically pure 36 (45%, 33% overall yield from 33) and
37 (43%, 31% from 33). The absolute structures of the amino
acids in 36 and 37 were determined by chiral HPLC analyses
of hydrolysates of compounds derived from 36 and 37, respec-
tively (vide infra). The primary hydroxy group in 36 was selec-
tively oxidized to give the carboxylic acid 38, whose N-Boc
group was deprotected to generate 6 as its TFA salt. Macrolac-
N
H
OH
c,d
26
+
NHBoc
H
H
HO2C
N
n-C13H27
O
O
OH
O
H
O
O
25
O
NHBoc
H
BzlO
N
N
H
tamization of 6 TFA by Shioiri’s procedure effectively con-
ꢂ
O
OH
structed the 13-membered cyclic structure, and compound 39
was obtained in 29% yield from 36. Deprotection of the O-
benzyl group in 39 by hydrogenolysis afforded a compound
possessing the proposed structure of stevastelin C3 (3) in
74% yield. At this stage, the absolute structures of the amino
acids in 3 were confirmed to all be L by chiral HPLC analyses
(MCI GEL CRS 10W, Mitsubishi Chemical Industries, Ltd.) of
acidic hydrolysates of 3. Similar HPLC analyses of hydroly-
sates of a de-O-benzyl product of compound 37 (prepared by
hydrogenolysis of 37 with H2, Pd/C in MeOH) showed that
the amino acids in 37 were D-serine, L-threonine, and L-valine.
The primary hydroxy group in 3 was selectively acetylated to
provide stevastelin B3 (2) in 38% yield.
27
n-C13H27
R1
O
O
O
OH
e
O
NHR2
H
26
H
BzlO
N
N
H
OH
28 : R1 = CH2OH, R2 = Boc
f
29 : R1 = CO2H, R2 = Boc
g
5•TFA : R1 = CO2H, R2 = H•CF3CO2H
The direct comparison of synthetic 2 and 3 with natural ste-
vastelins B3 and C3 revealed that synthetic 2 is unambiguous-
ly identical with natural stevastelin B3. Thus, the proposed
structure of stevastelin B3 was fully confirmed by this total
synthesis. However, spectral data of synthetic 3 were not
identical with those of natural stevastelin C3. Further analyses
of natural stevastelin C3 and compound 3 by 1H NMR (in
DMSO-d6) revealed that a proton of OH at C-5 (ꢁ ¼ 4:31)
and a methine proton attached to C-5 (ꢁ ¼ 3:85) observed in
compound 3 were missing in the spectrum of natural stevaste-
lin C3. The signal of a methine carbon bearing an oxygen
function (ꢁ ¼ 69:0) observed in the 13C NMR of compound
3 was also missing in the natural product. These results sug-
gested the possibility that the natural product might be a deoxy
derivative of the proposed structure. The molecular ion peak of
natural stevastelin C3 detected at m=z 598 (C32H59N3O7 þ H)
by FAB-MS also supported the deoxygenated structure [the
molecular ion peak of the proposed structure of stevastelin
C3 (3, C32H59N3O8 þ H) was observed at m=z 614].
n-C13H27
5
O
3
2
4
O
O
OH HN
h
O
H
N
H
RO
N
H
O
OH
30 : R = Bzl
31 : R = H
i
j
1 : R = Ac (stevastelin B)
Scheme 2. Cbz = –C(O)OCH2Ph, Boc = –C(O)OCMe3.
Reagents and conditions: a) 2-methoxypropene, CSA,
CH2Cl2; b) 2,4,6-trichlorobenzoyl chloride, Et3N, Cbz–
Ser(Bzl), THF then DMAP, toluene–THF; c) H2, 10%
Pd/C ethylenediamine complex, MeOH; d) Boc–Val–
Thr (25), WSC HCl, HOBt, DMF; e) aqueous AcOH;
ꢂ
f) TEMPO, KBr, NaOCl, NaHCO3, H2O–CH2Cl2, 0 ꢃC,
then NaClO2, HOSO2NH2, NaH2PO4, t-BuOH–H2O;
g) TFA, CH2Cl2, 0 ꢃC; h) DEPC, Et3N, DMF; i) H2,
20% Pd(OH)2/C, MeOH; j) Ac2O, pyridine, 0 ꢃC.
Total Synthesis and Structure Revision of Stevastelin C3.
To elucidate the correct structure of stevastelin C3, the natural
product was subjected to degradation (Scheme 4). Treatment
of natural stevastelin C3 with LiBH4 afforded the diol 42 in
24% yield. The structure of 42 was determined based on spec-
tral analyses, and finally confirmed by comparison with the
attempts, it was found that the modified Yamaguchi’s condi-
tions21b and Shiina’s method27 gave a condensate. Racemiza-
tion of the serine moiety during the coupling process was again
observed in this case, and 34 and its diastereoisomer were ob-

K. Kurosawa et al.
Bull. Chem. Soc. Jpn. Vol. 79, No. 6 (2006)
925
n-C13H27
BzlO
BzlO
OTES
n-C13H27
BzlO
OTES
n-C13H27
BzlO
e,f
a,b
d
23
O
O
BocHN
O
O
OH OR
BzlO
NHHN
32 : R = H
33 : R = TES
NHCbz
O
OH
c
H
O
34 + D-serine isomer
35 + D-serine isomer
n-C13H27
BzlO
OH
n-C13H27
OH
O
O
BzlO
BzlO
O
O
BocHN
BocHN
g
+
BzlO
NHHN
NHHN
O
OH
O
H
OH
H
O
O
36
37
n-C13H27
BzlO
BzlO
n-C13H27
5
O
3
4
2
CO2H
O
j
i
R1O
O
R2O
h
O
6•TFA
BocHN
O
HN
36
NHHN
NH HN
O
O
H
H
OH
O
O
OH
38
39
R
1 = R2 = Bzl
k
l
3 : R1 = R2 = H
(proposed structure of stevastelin C3)
2 : R1 = H, R2 = Ac (stevastelin B3)
Scheme 3. TES = –SiEt3. Reagents and conditions: a) (Me3Si)2NK, BzlBr, THF; b) aqueous AcOH; c) TESCl, Et3N, CH2Cl2;
d) Cbz–Ser(Bzl), 2,4,6-trichlorobenzoyl chloride, Et3N, DMAP, THF; e) H2, 10% Pd/C ethylenediamine complex, MeOH;
f) Boc–Val–Thr (25), WSC HCl, HOBt, DMF; g) AcOH–THF–H2O; h) TEMPO, KBr, NaOCl, NaHCO3, H2O–CH2Cl2, 0 ꢃC,
ꢂ
then NaClO2, HOSO2NH2, NaH2PO4, t-BuOH–H2O; i) TFA, CH2Cl2, 0 ꢃC; j) DEPC, Et3N, DMF; k) H2, 10% Pd/C, MeOH;
l) Ac2O, pyridine.
degradation studies, it was presumed that natural stevastelin
C3 is a 5-deoxy derivative of the proposed structure.
natural
stevastelin C3
6M aq HCl
L-serine, L-threonine, L-valine
110 °C
With this structural information, we turned to the synthesis
of the expected structure of stevastelin C3. The hydroxy group
in 23 was deoxygenated via the S-methyl dithiocarbonate ester
40 by Barton’s method28 to give 41 in 93% yield from 23. Acid
hydrolysis of 41 gave the diol 42 in 79% yield. The spectral
data of 42 were fully identical with those of the diol obtained
by reductive degradation of natural stevastelin C3. After selec-
tive protection of the primary hydroxy group in 42 as a TBS
ether, the resulting secondary alcohol in 43 was acylated with
Cbz–Ser(Bzl) under the modified Yamaguchi’s conditions to
give 44 and its D-serine isomer as an inseparable mixture in
a ratio of ca. 1.5:1 in 89% yield (Scheme 5). Condensation
of 43 with Cbz–Ser(Bzl) under Yamaguchi’s conditions gave
a 1:1 mixture of 44 and its epimer in 20% yield and that with
Shiina’s method also provided a 1:1 mixture in 87% yield. Hy-
drogenolysis of a mixture of 44 and its diastereomer, followed
by condensation with 25, afforded a mixture of 45 and its
D-serine isomer in 92% yield. Treatment of a mixture of 45
and its diastereomer with AcOH–H2O–THF, followed by chro-
matographic separation provided diastereomerically pure 46
(38% overall yield from 43) and 47 (25% from 43). The abso-
lute configurations of the amino acids in 46 and 47 were con-
firmed by chiral HPLC analyses of acidic hydrolysates of
de-O-benzyl products derived from 46 and 47, respectively.
LiBH4
1
5
3
n-C13H27
4
2
CH2OH
THF
OH
42
CSA
MeOH
5
n-C13H27
NaH, CS2, MeI
THF
23
R
O
O
Bu3SnH
AIBN
toluene
40 : R = OC(S)SMe
41 : R = H
Scheme 4.
synthetic specimen (vide infra). On the other hand, acid
hydrolysis of natural stevastelin C3, followed by chiral HPLC
analysis (MCI GEL CRS 10W) showed that the amino acids
constituting stevastelin C3 are the same as those of stevastelins
B and B3 (L-serine, L-threonine, and L-valine). From these

926 Bull. Chem. Soc. Jpn. Vol. 79, No. 6 (2006)
Total Synthesis of Stevastelins
n-C13H27
BzlO
CH2OTBS
n-C13H27
BzlO
CH2OTBS
c,d
O
O
a
b
n-C13H27
BocHN
42
CH2OTBS
O
O
OH
NH HN
NHCbz
O
43
H
O
OH
44 + D-serine isomer
45 + D-serine isomer
n-C13H27
OH
BocHN
NH HN
n-C13H27
OH
BocHN
NH HN
O
O
O
O
e
+
BzlO
BzlO
O
O
H
H
O
OH
O
OH
47
46
f,g
n-C13H27
BzlO
n-C13H27
O
5
3
CO2H
NH2•CF3CO2H
2
4
O
O
O
O
HN
h
RO
NH HN
O
NH HN
O
OH
H
H
O
O
OH
49 : R = Bzl
4 : R = H
48
i
(revised structure of stevastelin C3)
Scheme 5. TBS = –Si(Me)2(t-Bu). Reagents and conditions: a) TBSCl, Et3N, CH2Cl2; b) Cbz–Ser(Bzl), 2,4,6-trichlorobenzoyl
chloride, Et3N, DMAP, THF; c) H2, 10% Pd/C ethylenediamine complex, MeOH; d) Boc–Val–Thr (25), WSC HCl, HOBt,
ꢂ
DMF; e) AcOH–THF–H2O; f) TEMPO, KBr, NaOCl, NaHCO3, H2O–CH2Cl2, 0 ꢃC, then NaClO2, HOSO2NH2, NaH2PO4, t-
BuOH–H2O; g) TFA, CH2Cl2, 0 ꢃC; h) DEPC, Et3N, DMF; i) H2, 10% Pd/C, MeOH.
DIP-370 instrument with a 1 dm tube. Infrared (IR) spectra were
measured with a JASCO FT/IR-200 spectrometer and were re-
ported in wavenumbers (cmꢄ1). 1H NMR spectra were recorded at
270 MHz on a JEOL GSX-270, or at 300 MHz on a JEOL Lambda
300 or Varian MVX-300 spectrometer. Chemical shifts are report-
ed as ꢁ values in ppm relative to tetramethylsilane (ꢁ ¼ 0) or
chloroform (ꢁ ¼ 7:26). Coupling constants (J) are reported in
Hz. Abbreviations used are b (broad peak), s (singlet), d (doublet),
t (triplet), q (quartet), and m (complex multiplet). 13C NMR spec-
tra were recorded at 75 MHz on a JEOL Lambda 300 spectrome-
ter. Chemical shifts are reported as ꢁ values in ppm relative to
chloroform-d (ꢁ ¼ 77:00), DMSO-d6 (ꢁ ¼ 39:52), or methanol-
d4 (ꢁ ¼ 49:00) as internal references. Mass spectra were measured
by a JEOL GC Mate spectrometer in EI (70 eV) or FAB mode.
Organic extracts were dried over solid anhydrous Na2SO4 and
concentrated below 40 ꢃC under reduced pressure. Column chro-
matography was carried out with silica gel (Merck Kieselgel 60
Compound 46 was transformed into the macrocycle 49 via 48
in 28% overall yield by the same procedure as described for
preparation of 39 from 36. Removal of the O-benzyl group
in 49 furnished 4, whose spectral data as well as ½ꢀꢁD value
showed good accordance with those of natural stevastelin
C3. Based on this synthesis, it was concluded that the true
structure of natural stevastelin C3 is 4.
Conclusion
The total synthesis of stevastelins B, B3, C3, and the 5-de-
oxy derivative of stevastelin C3 from L-quebrachitol has been
accomplished. This study unambiguously confirmed the pro-
posed absolute structure of stevastelins B and B3, and revealed
that the structure of stevastelin C3 should be revised to the 5-
deoxy structure of the proposed one. Successful synthesis of
stevastelins also showed the usefulness of L-quebrachitol as
the starting material for chiral syntheses of natural products.
The methodology described here is applicable to the synthesis
of other stevastelins as well as other cyclic depsipeptides. It is
interesting to note that the fatty acid moiety of stevastelin C3 is
different from that of stevastelins B and B3, although the ste-
vastelins are produced by the same microorganism.
F
254; 230–400 mesh) for purification. Preparative TLC (PLC) was
performed with Merck PLC plates (Kieselgel 60 F254, 0.5 mm
thickness).
1-Deoxy-2-O-methyl-1-methylene-3,4:5,6-bis-O-(1-methyl-
ethylidene)-L-chiro-inositol (13). At 0 ꢃC, a THF solution (240
mL) of 2-O-methyl-3,4:5,6-bis-O-(1-methylethylidene)-L-chiro-1-
inosose (12) (10.5 g, 38.6 mmol), prepared from L-quebrachitol
by the method reported by Paulsen,16 was dropwise added to
a solution of Tebbe reagent15 [prepared by stirring a mixture of
[Cp2TiCl2] (25 g, 100 mmol) and Me3Al (2.0 M solution in tol-
uene, 100 mL, 200 mmol) under Ar at room temperature for 72 h],
Experimental
General. Melting points were determined on a Mitamura-
Riken micro hot stage and were not corrected. Optical rotations
were recorded using a sodium lamp (589 nm) with a JASCO

K. Kurosawa et al.
Bull. Chem. Soc. Jpn. Vol. 79, No. 6 (2006)
927
and the mixture was stirred at room temperature for 3 h. After di-
lution of the reaction mixture with Et2O (250 mL), 1 M aqueous
NaOH (200 mL) was slowly added to the resulting mixture at
0 ꢃC. The insoluble material was removed by filtration through
Celite. The layers were separated and the organic layer was wash-
ed with a 1 M aqueous NaOH solution and dried. Removal of the
solvent left a residue, which was purified by column chromatogra-
phy (silica gel, 200 g, EtOAc/hexane = 1/5 as eluent) to give
compound 13 (6.7 g, 64%) as white crystals: Rf ¼ 0:60 (EtOAc/
for 48 h. After addition of MeOH (10 mL), the reaction mixture
was concentrated to give a residue, which was purified by column
chromatography (silica gel, 90 g, EtOAc/toluene = 1/3 as eluent)
to give the 6-O-tosyl derivative 16 (2.32 g, 82%) as white crystals:
27
Rf ¼ 0:48 (acetone/toluene = 1/3); mp 120–122 ꢃC; ½ꢀꢁD ꢄ62
(c 1.4, CHCl3); IR (neat) 3450, 1355, 1175 cmꢄ1 1H NMR
;
(CDCl3, 270 MHz) ꢁ 1.21 (d, 3H, J ¼ 7:0 Hz), 1.29 and 1.45 (2s,
each 3H), 1.82 (ddq, 1H, J ¼ 4:0, 11.0, and 7.0 Hz), 2.44 (s, 3H),
3.15 (dd, 1H, J ¼ 9:2 and 11.0 Hz), 3.51 (dd, 1H, J ¼ 9:2 and
9.9 Hz), 3.60 (s, 3H), 3.97 (dd, 1H, J ¼ 4:8 and 7.3 Hz), 4.10
(dd, 1H, J ¼ 4:0 and 4.8 Hz), 4.66 (dd, 1H, J ¼ 7:3 and 9.9 Hz),
7.27–7.34 (m, 2H), 7.84–7.89 (m, 2H); 13C NMR (CDCl3, 75
MHz) ꢁ 13.6, 21.6, 25.9, 27.8, 35.3, 60.9, 73.8, 77.0, 77.6, 82.7,
85.9, 109.4, 128.1 (2C), 129.4 (2C), 134.2, 144.5; FAB-HRMS
Calcd for C18H27O7S ðM þ HÞþ: 387.1490, Found: m=z 387.1477.
Found: C, 55.67; H, 6.99%. Calcd for C18H26O7S: C, 55.94; H,
6.78%.
28
toluene = 1/3); mp 93–93.5 ꢃC (from EtOH); ½ꢀꢁD þ52 (c 0.8,
CHCl3); IR (neat) 1650 cmꢄ1; 1H NMR (CDCl3, 270 MHz) ꢁ 1.40,
1.44, 1.53, 1.59, and 3.46 (5s, each 3H), 3.57–3.61 (m, 2H), 4.01
(m, 1H), 4.32 (m, 1H), 4.77 (d, 1H, J ¼ 6:4 Hz), 5.41 and 5.56
(2d, each 1H, J ¼ 1:5 Hz); 13C NMR (CDCl3, 75 MHz) ꢁ 25.3,
27.0, 27.5, 57.0, 76.1, 77.0, 79.0, 79.2, 80.7, 110.6, 112.5, 118.7,
140.6; FAB-HRMS Calcd for C14H23O5 ðM þ HÞþ: 271.1546,
Found: m=z 271.1537. Found: C, 62.16; H, 7.97%. Calcd for
C14H22O5: C, 62.20; H, 8.20%.
1,2-Anhydro-5-deoxy-5-methyl-6-O-methyl-3,4-O-(1-methyl-
ethylidene)-D-epi-inositol (17). To a solution of the 6-O-tosyl
derivative 16 (2.32 g, 6.01 mmol) in MeOH (45 mL) at 0 ꢃC was
added NaOMe in MeOH (4.92 M, 2.50 mL, 12.3 mmol), and the
mixture was stirred at room temperature for 16 h. The reaction
mixture was neutralized by the addition of acetic acid (0.83 mL,
14.4 mmol) at 0 ꢃC, and then concentrated. The residue was dilut-
ed with EtOAc and washed with a saturated aqueous NaHCO3
solution and brine, and then dried. Removal of the solvent left a
residue, which was purified by column chromatography (silica
gel, 65 g, EtOAc/hexane = 1/5 as eluent) to give 17 (1.20 g,
93%) as white crystals: Rf ¼ 0:59 (acetone/toluene = 1/3); mp
1-Deoxy-2-O-methyl-1-methylene-3,4:5,6-bis-O-(1-methyl-
ethylidene)-L-chiro-inositol (14). To a stirred solution of com-
pound 13 (161 mg, 0.593 mmol) in MeOH (3 mL) at 0 ꢃC was
added p-toluenesulfonic acid monohydrate (p-TsOH, 1.1 mg, 5.9
mmol). After being stirred at 0 ꢃC for 5 h, the reaction mixture
was neutralized by the addition of triethylamine (0.5 mL) and con-
centrated to give a residue, which was purified by column chroma-
tography (silica gel, 4 g, EtOAc/toluene = 1/3 as eluent) to give
the starting material 13 (16 mg, 10%). Further elution with
MeOH/CHCl3 = 1/10 afforded the diol 14 (109 mg, 80%) as a
26
colorless syrup: Rf ¼ 0:51 (MeOH/CHCl3 = 1/10); ½ꢀꢁD ꢄ34
23
(c 1.6, CHCl3); IR (neat) 3450, 1650 cmꢄ1
;
1H NMR (CDCl3,
118.0–118.2 ꢃC; ½ꢀꢁD ꢄ52 (c 1.0, CHCl3); 1H NMR (CDCl3,
270 MHz) ꢁ 1.40 and 1.54 (2s, each 3H), 2.54 (m, 2H), 3.42
(dd, 1H, J ¼ 8:3 and 8.3 Hz), 3.49 (s, 3H), 3.76–3.88 (m, 2H),
4.08 (dd, 1H, J ¼ 5:9 and 6.3 Hz), 4.66 (d, 1H, J ¼ 5:9 Hz),
5.42 and 5.49 (2d, each 1H, J ¼ 1:5 Hz); FAB-HRMS Calcd for
C11H19O5 ðM þ HÞþ: 231.1233, Found: m=z 231.1236.
270 MHz) ꢁ 1.20 (d, 3H, J ¼ 7:0 Hz), 1.34 and 1.50 (2s, each 3H),
1.69 (ddq, 1H, J ¼ 2:9, 10.3, and 7.0 Hz), 3.20 (dd, 1H, J ¼ 3:7
and 3.8 Hz), 3.27 (d, 1H, J ¼ 10:3 Hz), 3.30 (d, 1H, J ¼ 3:8 Hz),
3.53 (s, 3H), 4.13 (dd, 1H, J ¼ 2:9 and 6.4 Hz), 4.39 (dd, 1H, J ¼
3:7 and 6.4 Hz); 13C NMR (CDCl3, 75 MHz) ꢁ 14.9, 25.3, 25.7,
35.2, 51.4, 57.1, 57.6, 72.2, 75.9, 76.9, 109.1; FAB-HRMS Calcd
for C11H19O4 ðM þ HÞþ: 215.1283, Found m=z 215.1273. Found:
C, 61.43; H, 8.77%. Calcd for C11H18O4: C, 61.66; H, 8.47%.
4,6-Dideoxy-4,6-dimethyl-5-O-methyl-2,3-O-(1-methylethyl-
idene)-D-allo-inositol (18). To a solution of the epoxide 17 (2.07
g, 9.38 mmol) in CH2Cl2 (193 mL) at room temperature under Ar
was added Me3Al (1.0 M solution in hexane, 96.6 mL, 96.6 mmol)
via a cannula, and the mixture was stirred at room temperature for
19 h. To the reaction mixture was added H2O (10 mL) at 0 ꢃC, and
the mixture was diluted with EtOAc. The organic layer was wash-
ed successively with a 0.5 M aqueous HCl solution, a saturated
aqueous NaHCO3 solution and brine, and then dried. Removal
of the solvent left a syrup, which was purified by column chroma-
tography (silica gel, 60 g, EtOAc/hexane = 1/6 as eluent) to give
the alcohol 18 (2.00 g, 93%) as a colorless syrup: Rf ¼ 0:47 (ace-
3-Deoxy-3-methyl-4-O-methyl-1,2-O-(1-methylethylidene)-D-
myo-inositol (15). A mixture of the alkene 14 (6.81 g, 29.6
mmol) and Raney-Ni W-4 (ca. 50 mL) in EtOH (205 mL) was hy-
drogenated under an atmospheric pressure of H2 at room temper-
ature for 3 h. The insoluble material was removed by filtration and
the filtrate was concentrated to give a residue, which was purified
by column chromatography (silica gel, 400 g, acetone/toluene =
1/3 as eluent) to afford compound 15 (6.50 g, 95%) as white crys-
tals: Rf ¼ 0:45 (MeOH/CHCl3 = 1/10); mp 131–133 ꢃC (from
27
EtOH); ½ꢀꢁD ꢄ35 (c 1.1, CHCl3); IR (neat) 3450 cmꢄ1; 1H NMR
(CDCl3, 270 MHz) ꢁ 1.24 (d, 3H, J ¼ 6:8 Hz), 1.35 and 1.51 (2s,
each 3H), 1.85 (m, 1H), 2.68–2.80 (m, 2H), 3.08 (dd, 1H, J ¼ 9:3
and 10.7 Hz), 3.33 (dd, 1H, J ¼ 9:3 and 9.8 Hz), 3.58 (s, 3H), 3.64
(dd, 1H, J ¼ 7:8 and 9.8 Hz), 3.91 (dd, 1H, J ¼ 4:9 and 7.8 Hz),
4.12 (dd, 1H, J ¼ 3:9 and 4.9 Hz); 13C NMR (CD3OD, 75 MHz)
ꢁ 14.3, 26.4, 28.8, 39.1, 60.6, 74.7, 76.9, 79.0, 81.4, 84.5, 109.8;
FAB-HRMS Calcd for C11H21O5 ðM þ HÞþ: 233.1389, Found:
m=z 233.1407. Found: C, 56.66; H, 8.44%. Calcd for C11H20O5:
C, 56.88; H, 8.68%.
20
tone/toluene = 1/5); ½ꢀꢁD ꢄ2:7 (c 1.2, CHCl3); IR (neat) 3460
cmꢄ1
;
1H NMR (CDCl3, 300 MHz) ꢁ 0.99 (d, 3H, J ¼ 6:9 Hz),
1.16 (d, 3H, J ¼ 7:2 Hz), 1.36 and 1.50 (2s, each 3H), 1.81 (ddq,
1H, J ¼ 1:5, 9.6, and 7.2 Hz), 2.13 (d, 1H, J ¼ 6:3 Hz), 2.27 (ddq,
1H, J ¼ 6:9, 6.0, and 7.3 Hz), 3.33 (dd, 1H, J ¼ 9:6 and 6.0 Hz),
3.40 (s, 3H), 3.59 (m, 1H), 4.28 (m, 2H); 13C NMR (CDCl3,
75 MHz) ꢁ 10.7, 15.0, 24.5, 26.0, 33.5, 34.6, 59.0, 70.8, 74.5,
77.2, 80.3, 108.4; FAB-HRMS calcd for C12H23O4 ðM þ HÞþ:
231.1596, Found: m=z 231.1602. Found: C, 62.49; H, 9.62%.
Calcd for C12H22O4: C, 62.58; H, 9.63%.
3-Deoxy-3-methyl-4-O-methyl-6-O-(4-methylphenylsulfonyl)-
1,2-O-(1-methylethylidene)-D-myo-inositol (16). A mixture of
15 (1.70 g, 7.32 mmol) and n-Bu2SnO (2.19 g, 14.6 mmol) in
MeOH (200 mL) was heated under reflux for 40 h. The reaction
mixture was cooled to room temperature and concentrated to give
a residue, which was dissolved in 1,4-dioxane (100 mL). To this
solution were added TsCl (1.67 g, 14.6 mmol) and DMAP (179
mg, 1.46 mmol), and the mixture was stirred at room temperature
1-O-Benzoyl-4,6-dideoxy-4,6-dimethyl-5-O-methyl-2,3-O-(1-
methylethylidene)-D-allo-inositol (19). To a solution of com-

928 Bull. Chem. Soc. Jpn. Vol. 79, No. 6 (2006)
Total Synthesis of Stevastelins
pound 18 (99 mg, 0.43 mmol) in pyridine (2 mL) were added ben-
zoyl chloride (0.17 mL, 1.46 mmol) and DMAP (12 mg, 0.098
mmol), and the mixture was stirred at room temperature for 9 h.
After addition of MeOH (1 mL) at 0 ꢃC, the reaction mixture was
concentrated to give a residue, which was diluted with EtOAc.
The organic layer was washed successively with a 1 M aqueous
HCl solution, a saturated aqueous NaHCO3 solution and brine,
and then dried. Removal of the solvent left a syrup, which was
purified by column chromatography (silica gel, 10 g, EtOAc/
hexane = 1/10 as eluent) to give the benzoate 19 (92 mg, 64%)
(708 mg, 2.90 mmol) in THF (28 mL) at 0 ꢃC was added LiAlH4
(547 mg, 14.5 mmol), and the mixture was stirred at room temper-
ature for 2 h. To the ice-cooled reaction mixture was added H2O
(20 mL) dropwise, and then the mixture was diluted with MeOH.
The insoluble material was removed by filtration through Celite,
and the filtrate was concentrated to give a residue, which was dis-
solved in pyridine (30 mL). To this solution at 0 ꢃC were added
2,2-dimethylpropanoyl chloride (PivCl, 0.88 mL, 7.2 mmol) and
DMAP (354 mg, 2.90 mmol), and the mixture was stirred at room
temperature for 2 h. After the addition of MeOH (5 mL) at 0 ꢃC,
the reaction mixture was concentrated to give a residue, which
was diluted with EtOAc and washed successively with a 1 M
aqueous HCl solution, a saturated aqueous NaHCO3 solution
and brine, and then dried. Removal of the solvent left a residue,
which was purified by column chromatography (silica gel, 20 g,
EtOAc/hexane = 1/6 as eluent) to afford the di-O-pivaloyl deriv-
ative 20 (679 mg, 65%) as colorless crystals: Rf ¼ 0:41 (EtOAc/
25
as a colorless syrup: Rf ¼ 0:55 (EtOAc/hexane = 1/3); ½ꢀꢁD
ꢄ15 (c 1.3, CHCl3); IR (neat) 1720 cmꢄ1
;
1H NMR (CDCl3,
270 MHz) ꢁ 1.01 (d, 3H, J ¼ 7:3 Hz), 1.17 (d, 3H, J ¼ 7:0 Hz),
1.30 and 1.45 (2s, each 3H), 1.87 (ddq, 1H, J ¼ 3:7, 7.0, and
7.0 Hz), 2.67 (ddq, 1H, J ¼ 7:0, 9.2, and 7.3 Hz), 3.40 (s, 3H),
3.42 (dd, 1H, J ¼ 7:0 and 7.0 Hz), 4.31 (dd, 1H, J ¼ 3:7 and
7.3 Hz), 4.54 (dd, 1H, J ¼ 3:7 and 7.3 Hz), 5.08 (dd, 1H, J ¼
3:7 and 9.2 Hz), 7.42–7.60 (m, 3H), 8.08–8.12 (m, 2H). Found:
C, 67.98; H, 8.04%. Calcd for C19H26O5: C, 68.24; H, 7.84%.
(3aR,5R,6R,7R,7aR)-Tetrahydro-6-methoxy-2,2,5,7-tetra-
methyl-1,3-benzodioxol-4(3aH)-one (10). To a solution of the
alcohol 18 (616 mg, 2.67 mmol) in CH2Cl2 (30 mL) at 0 ꢃC was
added PCC on alumina (1 mmol gꢄ1, 14.4 g, 14.4 mmol). After be-
ing stirred at room temperature for 4 h, the reaction mixture was
diluted with Et2O and the insoluble material was removed by fil-
tration through Celite. The filtrate was concentrated to give the
crude ketone 10 (610 mg), which was used in the next reaction
without further purification. A part of this compound was purified
by column chromatography and used as an analytical sample: Rf ¼
24
hexane = 1/3); mp 61.0–62.7 ꢃC; ½ꢀꢁD ꢄ15 (c 1.3, CHCl3); IR
(neat) 1715 cmꢄ1; 1H NMR (CDCl3, 300 MHz) ꢁ 0.88 (d, 3H, J ¼
6:8 Hz), 0.90 (d, 3H, J ¼ 6:8 Hz), 1.22 and 1.24 (2s, each 9H),
1.78 (ddq, 1H, J ¼ 9:2, 2.0, and 6.8 Hz), 2.01 (dddq, 1H, J ¼ 9:6,
3.4, 5.6, and 6.8 Hz), 2.63 (bs, 1H), 3.46 (s, 3H), 3.52 (dd. 1H, J ¼
2:0 and 9.6 Hz), 3.79 (ddd, 1H, J ¼ 9:2, 6.3, and 2.9 Hz), 4.08 (dd,
1H, J ¼ 5:6 and 10.7 Hz), 4.09 (dd, 1H, J ¼ 6:3 and 11.5 Hz),
4.22 (dd, 1H, J ¼ 10:7 and 3.4 Hz), 4.34 (dd, 1H, J ¼ 11:5 and
2.9 Hz); 13C NMR (CDCl3, 75 MHz) ꢁ 9.3, 14.2, 27.11 (3C), 27.13
(3C), 35.7, 37.3, 38.8, 60.5, 66.4, 67.5, 71.6, 81.1, 178.5, 178.8;
FAB-HRMS Calcd for C19H37O6 ðM þ HÞþ: 361.2590, Found
m=z 361.2579. Found: C, 63.19; H, 9.99%. Calcd for C19H36O6:
C, 63.30; H, 10.07%.
0:67 (acetone/toluene = 1/3); IR (neat) 1730 cmꢄ1 1H NMR
;
(CDCl3, 300 MHz) ꢁ 1.09 (d, 3H, J ¼ 7:3 Hz), 1.18 (d, 3H, J ¼
7:1 Hz), 1.32 and 1.36 (2s, each 3H), 2.29 (ddq, 1H, J ¼ 7:1, 4.2,
and 10.0 Hz), 2.99 (dq, 1H, J ¼ 4:6 and 7.3 Hz), 3.31 (s, 3H), 3.34
(dd, 1H, J ¼ 4:6 and 10.0 Hz), 4.29 (dd, 1H, J ¼ 5:4 and 4.2 Hz),
4.45 (d, 1H, J ¼ 5:4 Hz); 13C NMR (CDCl3, 75 MHz) ꢁ 9.7, 13.7,
25.7, 26.9, 32.3, 46.2, 57.2, 70.0, 78.0, 80.4, 109.4, 210.2; FAB-
HRMS Calcd for C12H21O4 ðM þ HÞþ: 229.1440, Found m=z
229.1457. Found: C, 62.93; H, 8.54%. Calcd for C12H20O4: C,
63.14; H, 8.83%.
1,6-Bis-O-(2,2-dimethylpropanoyl)-2,4-dideoxy-2,4-dimethyl-
5-O-methylsulfonyl-3-O-methyl-L-mannitol (21). To a solution
of the pivalate 20 (655 mg, 1.82 mmol) in pyridine (16 mL) at 0 ꢃC
was added MsCl (0.70 mL, 9.08 mmol), and the mixture was stir-
red at room temperature for 6 h. The reaction mixture was concen-
trated to give a residue, which was diluted with EtOAc. The or-
ganic layer was washed successively with a 1 M aqueous HCl so-
lution, a saturated aqueous NaHCO3 solution and brine, and then
dried. Removal of the solvent left a residue, which was purified by
column chromatography (silica gel, 20 g, EtOAc/hexane = 1/7
as eluent) to afford 21 (788 mg, 99%) as a colorless syrup: Rf ¼
3,5-Dideoxy-3,5-dimethyl-4-O-methyl-1,2-O-(1-methylethyl-
idene)-6-C-oxo-ꢀ-L-mannoseptanose (9). To a solution of the
crude ketone 10 (610 mg, 2.67 mmol) in (CH2Cl)2 (30 mL) at 0 ꢃC
were added mCPBA (692 mg, 4.01 mmol) and KHCO3 (401 mg,
4.01 mmol), and the mixture was stirred at room temperature for
5 h. The reaction mixture was diluted with CHCl3 and then wash-
ed successively with a 20% aqueous NaHSO3 solution, a saturated
aqueous NaHCO3 solution and brine, and then dried. Removal of
the solvent gave a residue, which was purified by column chroma-
tography (silica gel, 15 g, EtOAc/hexane = 1/7 as eluent) to af-
ford 9 (529 mg, 81% from 18) as a colorless syrup: Rf ¼ 0:80
23
0:16 (EtOAc/hexane = 1/5); ½ꢀꢁD ꢄ13 (c 1.9, CHCl3); IR
(neat) 1730, 1360, 1160 cmꢄ1; 1H NMR (CDCl3, 300 MHz) ꢁ 0.93
(d, 3H, J ¼ 6:8 Hz), 0.96 (d, 3H, J ¼ 7:1 Hz), 1.23 and 1.24 (2s,
each 9H), 2.01 (m, 1H), 2.13 (ddq, 1H, J ¼ 1:7, 8.0, and 7.1 Hz),
3.09 (s, 3H), 3.35 (dd, 1H, J3;4 ¼ 1:7 and 9.0 Hz), 3.48 (s, 3H),
4.08 (dd, 1H, J ¼ 5:2 and 10.9 Hz), 4.11 (dd, 1H, J ¼ 5:0 and
13.1 Hz), 4.21 (dd, 1H, J ¼ 3:5 and 10.9 Hz), 4.69 (dd, 1H, J ¼
2:0 and 13.1 Hz), 4.91 (ddd, 1H, J ¼ 2:0, 5.0, and 8.0 Hz);
13C NMR (CDCl3, 75 MHz) ꢁ 8.6, 14.2, 27.1 (3C), 27.2 (3C),
35.9, 37.1, 38.9, 39.3, 60.8, 63.2, 66.0, 80.9, 82.4, 178.0, 178.4;
FAB-HRMS Calcd for C20H39O8S ðM þ HÞþ: 439.2365, Found
m=z 439.2373.
1,2-Anhydro-3,5-dideoxy-6-O-(2,2-dimethylpropanoyl)-3,5-
dimethyl-4-O-methyl-L-glucitol (8). To a solution of the mesy-
late 21 (321 mg, 0.732 mmol) in MeOH (17 mL) at 0 ꢃC was added
MeONa in MeOH (4.92 M, 0.45 mL, 2.21 mmol), and the mixture
was stirred at room temperature for 3 h. To the reaction mixture
was added AcOH (0.17 mL) at 0 ꢃC, and the mixture was concen-
trated to give a residue, which was purified by column chromatog-
raphy (silica gel, 15 g, EtOAc/hexane = 1/5 as eluent) to afford 8
(182 mg, 96%) as a colorless syrup: Rf ¼ 0:55 (EtOAc/hexane =
24
(acetone/toluene = 1/1); ½ꢀꢁD ꢄ122 (c 1.0, CHCl3); IR (neat)
1755 cmꢄ1
;
1H NMR (CDCl3, 300 MHz) ꢁ 1.29 (d, 3H, J ¼ 6:8
Hz), 1.33 (d, 3H, J ¼ 6:8 Hz), 1.35 and 1.56 (2s, each 3H), 1.94
(dq, 1H, J ¼ 8:5 and 6.8 Hz), 3.16 (dd, 1H, J ¼ 4:6 and 8.5 Hz),
3.31 (dq, 1H, J ¼ 4:6 and 6.8 Hz), 3.51 (s, 3H), 4.23 (d, 1H, J ¼
6:8 Hz), 5.72 (d, 1H, J ¼ 6:8 Hz); 13C NMR (CDCl3, 75 MHz) ꢁ
12.6, 18.5, 23.9, 25.3, 37.4, 40.9, 61.6, 79.4, 83.1, 99.3, 108.9,
172.5; EI-HRMS Calcd for C12H20O5 Mþ: 244.1311, Found
m=z 244.1317. Found: C, 58.93; H, 8.15%. Calcd for C12H20O5:
C, 59.00; H, 8.25%.
1,6-Bis-O-(2,2-dimethylpropanoyl)-2,4-dideoxy-2,4-dimethyl-
3-O-methyl-L-mannitol (20). To a solution of the lactone 9

K. Kurosawa et al.
Bull. Chem. Soc. Jpn. Vol. 79, No. 6 (2006)
929
24
1/3); ½ꢀꢁD ꢄ21 (c 2.0, CHCl3); IR (neat) 1730 cmꢄ1; H NMR
(CDCl3, 300 MHz) ꢁ 0.92 (d, 3H, J ¼ 6:8 Hz), 1.07 (d, 3H, J ¼
7:1 Hz), 1.22 (s, 9H), 1.44 (ddq, 1H, J ¼ 3:4, 7.3, and 6.8 Hz),
2.02 (m, 1H), 2.60 (dd, 1H, J ¼ 2:7 and 4.9 Hz), 2.82 (dd, 1H, J ¼
3:9 and 4.9 Hz), 2.95 (ddd, 1H, J ¼ 2:7, 3.9, and 7.3 Hz), 3.06
(dd, 1H, J ¼ 3:4 and 8.3 Hz), 3.42 (s, 3H), 4.04 (dd, 1H, J ¼ 6:1
and 10.7 Hz) and 4.20 (dd, 1H, J ¼ 3:7 and 10.7 Hz); 13C NMR
(CDCl3, 75 MHz) ꢁ 10.7, 14.4, 27.2 (3C), 35.6, 38.9, 39.1, 46.8,
55.6, 60.6, 65.9, 84.7, 178.4; EI-HRMS Calcd for C14H27O4
ðM þ HÞþ: 259.1909, Found m=z 259.1916. Found: C, 65.02; H,
10.15%. Calcd for C14H26O4: C, 65.09; H, 10.14%.
(ꢁR,ꢀS,4S,5S)-ꢀ,2,2,5-Tetramethyl-ꢁ-tridecyl-1,3-dioxane-
4-ethanol (23). To a solution of the triol 7 (267 mg, 0.808 mmol)
in CH2Cl2 (28 mL) at room temperature were added 2-methoxy-
propene (0.155 mL, 1.62 mmol) and CSA (19 mg, 0.081 mmol),
and the mixture was stirred at room temperature for 5 min. To
the reaction mixture at 0 ꢃC was added Et3N (4 mL), and the mix-
ture was diluted with EtOAc. The organic layer was washed with a
saturated aqueous NaHCO3 solution and brine, and then dried. Re-
moval of the solvent left a residue, which was purified by column
chromatography (silica gel, 30 g, EtOAc/hexane = 1/14 as elu-
ent) to afford 23 (229 mg, 76%) as a colorless syrup: Rf ¼ 0:68
1
21
(2S,3S,4S,5R)-3-Methoxy-2,4-dimethyl-1,5-octadecanediol (22).
To a stirred mixture of the epoxide 8 (532 mg, 2.06 mmol) and
CuCN (92 mg, 1.0 mmol) in Et2O at 0 ꢃC under Ar was added a
solution of didodecylmagnesium18 [1.0 M solution in Et2O, 10.3
mL, 10.3 mmol; prepared by addition of 1,4-dioxane (1.26 mL,
14.8 mmol) to a 1 M solution of dodecylmagnesium bromide in di-
ethyl ether (15 mL), followed by centrifuging (2500 rpm, 10 min)],
and the mixture was stirred at room temperature for 2 h. The reac-
tion mixture was quenched by the addition of a saturated aqueous
NH4Cl solution at 0 ꢃC, and the products were extracted with
EtOAc. The organic layer was washed with a saturated aqueous
NaHCO3 solution and brine, and then dried. Removal of the sol-
vent left a residue, which was purified by column chromatography
(silica gel, 30 g, EtOAc/hexane = 1/7 as eluent) to afford 22 (618
mg, 87%) as a colorless syrup: Rf ¼ 0:50 (acetone/toluene =
(EtOAc/hexane = 1/3); ½ꢀꢁD þ35 (c 1.2, CHCl3); IR (neat)
3540 cmꢄ1
;
1H NMR (CDCl3, 300 MHz) ꢁ 0.71 (d, 3H, J ¼ 6:6
Hz), 0.88 (t, 3H, J ¼ 6:7 Hz), 0.93 (d, 3H, J ¼ 7:1 Hz), 1.22–1.34
(m, 24H), 1.37 and 1.48 (2s, each 3H), 1.68 and 1.92 (2m, each
1H), 3.39 (bs, 1H), 3.53 (dd, 1H, J ¼ 11:3 and 11.4 Hz), 3.70 (dd,
1H, J ¼ 5:3 and 11.4 Hz), 3.73 (dd, 1H, J ¼ 2:0 and 10.4 Hz),
3.77 (m, 1H); 13C NMR (CDCl3, 75 MHz) ꢁ 4.8, 12.0, 14.1, 19.2,
22.7, 26.2, 29.3, 29.6, 29.7, 30.5, 31.9, 35.0, 36.8, 66.1, 76.7, 81.4,
98.2; EI-HRMS Calcd for C23H46O3 Mþ: 370.3447, Found m=z
370.3444. Found: C, 74.52; H, 12.48%. Calcd for C23H46O3: C,
74.54; H, 12.51%.
An Inseparable Mixture of N-[(Phenylmethoxy)carbonyl]-
O-(phenylmethyl)-L-serine (1R)-1-[(1S)-1-[(4S,5S)-2,2,5-Tri-
methyl-1,3-dioxan-4-yl]ethyl]tetradecyl Ester (24) and Its D-
Serine Isomer. To a solution of N-[(phenylmethoxy)carbon-
yl]-O-(phenylmethyl)-L-serine [Cbz–Ser(Bzl),22 244 mg, 0.741
mmol] in THF (2 mL) under Ar at 0 ꢃC were added 2,4,6-trichlo-
robenzoyl chloride (0.116 mL, 0.742 mmol) and Et3N (0.104 mL,
0.742 mmol). After being stirred at room temperature for 1 h,
the reaction mixture was diluted with toluene (7 mL) and centri-
fuged (3000 rpm, 10 min). The supernatant layer was added to a
solution of the alcohol 19 (55 mg, 0.15 mmol) in toluene (5.5 mL)
at 0 ꢃC under Ar via a cannula. To this mixture under Ar at 0 ꢃC
was added a solution of DMAP (14.5 mg, 0.119 mmol) in toluene
(2 mL) dropwise over 1.5 h, and the resulting mixture was further
stirred at 0 ꢃC for 40 min. To the reaction mixture was added a 1 M
aqueous citric acid solution, and the products were extracted with
EtOAc. The organic layer was washed with a saturated aqueous
NaHCO3 solution and brine, and then dried. Removal of the sol-
vent left a residue, which was purified by column chromatography
(silica gel, 5 g, EtOAc/hexane = 1/14 as eluent) to afford an in-
separable mixture (ca. 6:1) of 24 and its D-serine isomer (74 mg,
73%) as a colorless syrup: Rf ¼ 0:60 (EtOAc/hexane = 1/3); IR
24
1/3); ½ꢀꢁD þ7:5 (c 0.9, CHCl3); IR (neat) 3420 cmꢄ1; H NMR
(CDCl3, 300 MHz) ꢁ 0.88 (t, 3H, J ¼ 6:8 Hz), 0.94 (d, 3H, J ¼
6:8 Hz), 0.96 (d, 3H, J ¼ 6:6 Hz), 1.21–1.34 (m, 22H), 1.45 (m,
2H), 1.71 (ddq, 1H, J ¼ 1:7, 4.1, and 6.8 Hz), 1.98 (m, 1H), 3.28
(dd, 1H, J ¼ 4:1 and 7.5 Hz), 3.51 (s, 3H), 3.66 (dd, 1H, J ¼ 5:6
and 11.0 Hz), 3.71 (dd, 1H, J ¼ 4:4 and 11.0 Hz), 3.73 (m, 1H,
H-5); 13C NMR (CDCl3, 75 MHz) ꢁ 7.2, 14.0, 14.4, 22.6, 26.2,
29.3, 29.6, 29.7, 31.9, 35.0, 37.5, 39.3, 60.4, 65.1, 74.6, 88.8;
FAB-HRMS Calcd for C21H45O3 ðM þ HÞþ: 345.3369, Found
m=z 345.3374. Found: C, 73.15; H, 12.75%. Calcd for C21H44O3:
C, 73.20; H, 12.87%.
1
(2S,3S,4S,5R)-2,4-Dimethyl-1,3,5-octadecanetriol (7). To a
solution of the methyl ether 22 (443 mg, 1.28 mmol) in CH2Cl2
(22 mL) at ꢄ18 ꢃC under Ar was added iodotrimethylsilane19 [pre-
pared by heating a mixture of hexamethyldisilane (2.05 mL, 10
mmol) and iodine (2.5 g, 10 mmol) at 65 ꢃC for 1.5 h]. After being
stirred at room temperature for 2 h, to the reaction mixture was
added MeOH at 0 ꢃC. The mixture was diluted with EtOAc and
washed successively with a 20% aqueous Na2S2O3 solution, a sat-
urated aqueous NaHCO3 solution and brine, and then dried. Re-
moval of the solvent left a residue, which was purified by column
chromatography (silica gel, 7 g, EtOAc/hexane = 1/2 as eluent)
to afford 7 (394 mg, 93%) as an amorphous solid: Rf ¼ 0:42
1
(neat) 3300–3500, 1730, 1705 cmꢄ1; H NMR (CDCl3, 300 MHz
for the major isomer 24) ꢁ 0.67 (d, 3H, J ¼ 6:6 Hz), 0.88 (t, 3H,
J ¼ 6:8 Hz), 0.90 (d, 3H, J ¼ 6:8 Hz), 1.18–1.60 (m, 24H), 1.30
and 1.36 (2s, each 3H), 1.78–1.87 (m, 2H), 3.48 (dd, 1H, J ¼ 11:0
and 11.5 Hz), 3.57 (dd, 1H, J ¼ 1:0 and 10.0 Hz), 3.67 (dd, 1H,
J ¼ 4:9 and 11.5 Hz), 3.72 (dd, 1H, J ¼ 3:2 and 9.3 Hz), 3.92
(dd, 1H, J ¼ 2:7 and 9.3 Hz), 4.44–4.51 (m, 3H), 5.03 (m, 1H),
5.12 (s, 2H), 5.68 (bd, 1H, J ¼ 8:5 Hz), 7.24–7.37 (m, 10H);
FAB-HRMS Calcd for C41H64NO7 ðM þ HÞþ: 682.4683, Found
m=z 682.4689.
22
(acetone/toluene = 1/3); mp 54.5–56.0 ꢃC; ½ꢀꢁD þ17 (c 1.3,
20
CHCl3), {lit.,3 ½ꢀꢁD þ14:1 (c 1.23, CHCl3)}; IR (neat) 3250
cmꢄ1
;
1H NMR (CDCl3, 300 MHz) ꢁ 0.75 (d, 3H, J ¼ 6:8 Hz),
0.88 (t, 3H, J ¼ 6:8 Hz), 0.92 (d, 3H, J ¼ 7:1 Hz), 1.22–1.69
(m, 25H), 1.89 (m, 1H), 2.83 and 3.39 (2bs, each 1H), 3.63–3.73
(m, 2H), 3.76 (dd, 1H, J ¼ 1:5 and 9.5 Hz), 3.87 (m, 1H), 4.39 (bs,
1H); 13C NMR (CDCl3, 75 MHz) ꢁ 4.0, 13.1, 14.1, 22.6, 26.0,
29.3, 29.6, 29.6, 31.9, 35.4, 37.2, 37.7, 69.1, 77.7, 83.5; FAB-
HRMS Calcd for C20H43O3 ðM þ HÞþ: 331.3212, Found m=z
331.3201. Found: C, 72.53; H, 12.52%. Calcd for C20H42O3: C,
72.67; H, 12.81%. The 1H NMR data were identical to those
reported for the authentic compound derived from natural stevas-
telin B by reductive degradation.3
Boc–Thr(Bzl)–OBzl.
To a solution of [N-(1,1-dimethyl-
ethoxy)carbonyl]-O-(phenylmethyl)-L-threonine [Boc–Thr(Bzl);
purchased from Peptide Institute, Inc., Osaka, Japan] (1.00 g,
3.23 mmol) in DMF (15 mL) at 0 ꢃC were added Et3N (0.45 mL,
3.23 mmol) and benzyl bromide (0.383 mL, 3.23 mmol), and the
mixture was stirred at room temperature for 12 h. The reaction
mixture was diluted with EtOAc, and washed successively with
a 1 M aqueous citric acid solution, a saturated aqueous NaHCO3

930 Bull. Chem. Soc. Jpn. Vol. 79, No. 6 (2006)
Total Synthesis of Stevastelins
solution and brine, and then dried. Removal of the solvent left a
residue, which was purified by column chromatography (silica
gel, 20 g, EtOAc/hexane = 1/8 as eluent) to afford the title com-
pound (1.10 g, 85%) as a colorless syrup: Rf ¼ 0:61 (EtOAc/
(27). A mixture of the acetonide 24 and its D-serine isomer (ca.
6:1, 23 mg, 0.034 mmol) in MeOH (4.5 mL) was stirred in the
presence of 10% Pd on a carbon ethylenediamine complex24
(23 mg) under an atmospheric pressure of H2 at room temperature
for 1 h. The insoluble material was removed by filtration and the
filtrate was concentrated to give a crude amine, which was dis-
solved in DMF (1.9 mL). To this solution at 0 ꢃC were added
23
hexane = 1/3); ½ꢀꢁD ꢄ18 (c 0.7, CHCl3); IR (neat) 3450, 1750,
1710 cmꢄ1
;
1H NMR (CDCl3, 300 MHz) ꢁ 1.25 (d, 3H, J ¼ 6:6
Hz), 1.44 (s, 9H), 4.14 (dq, 1H, J ¼ 2:2 and 6.6 Hz,), 4.34 (dd, 1H,
J ¼ 2:2 and 9.7 Hz), 4.26 and 4.47 (2d, each 1H, J ¼ 11:7 Hz),
5.12 (s, 2H), 5.30 (d, 1H, J ¼ 9:7 Hz), 7.15–7.33 (m, 10H);
13C NMR (CDCl3, 75 MHz) ꢁ 16.1, 28.1, 58.2, 66.9, 70.7, 74.4,
79.6, 127.4, 128.2, 128.32, 128.35, 129.2, 135.2, 137.7, 156.0,
170.8; FAB-HRMS Calcd for C23H30NO5 ðM þ HÞþ: 400.2124,
Found m=z 400.2113. Found: C, 68.90; H, 7.26; N, 3.45%. Calcd
for C23H29NO5: C, 69.15; H, 7.32; N, 3.51%.
the dipeptide 25 (17 mg, 0.053 mmol), WSC HCl (32 mg, 0.17
ꢂ
mmol), and HOBt (23 mg, 0.17 mmol), and the whole mixture
was stirred at room temperature for 14 h. The reaction mixture
was diluted with EtOAc and washed successively with a 1 M
aqueous citric acid solution, a saturated aqueous NaHCO3 solution
and brine, and then dried. Removal of the solvent left a residue,
which was purified by column chromatography (silica gel, 5 g,
acetone/toluene = 1/10 as eluent) to first afford 27 (3.7 mg, 13%)
Boc–Val–Thr(Bzl)–OBzl.
Boc–Thr(Bzl)–OBzl (1.10 g,
22
2.75 mmol) was dissolved in TFA (5 mL) at 0 ꢃC, and the solution
was stirred at room temperature for 1 h. The reaction mixture was
concentrated to give a residue, which was dissolved in HCl in 1,4-
dioxane (6 M solution, 1 mL). The mixture was concentrated and
dried in vacuo to afford Thr(Bzl)–OBzl HCl salt (985 mg). To a
solution of [N-(1,1-dimethylethoxy)carbonyl]-L-valine (Boc–Val;
purchased from Peptide Institute, Inc., Osaka, Japan) (1.50 g,
6.88 mmol) in DMF (10 mL) at ꢄ18 ꢃC were added a solution of
Thr(Bzl)–OBzl HCl salt (985 mg, 2.75 mmol) in DMF (10 mL),
as a colorless syrup: Rf ¼ 0:50 (acetone/toluene = 1/4); ½ꢀꢁD
ꢄ23 (c 0.7, CHCl3); IR (neat) 3300, 1740, 1715, 1645 cmꢄ1
;
1H NMR (CDCl3, 300 MHz) ꢁ 0.66 and 0.85 (2d, each 3H, J ¼
6:6 Hz), 0.88 (t, 3H, J ¼ 6:8 Hz), 0.90 (d, 3H, J ¼ 6:8 Hz), 0.96
(d, 3H, J ¼ 6:6 Hz), 1.14–1.70 (m, 24H), 1.17 (d, 3H, J ¼ 6:3
Hz), 1.33 and 1.39 (2s, each 3H), 1.43 (s, 9H), 1.70–1.92 (m,
2H), 2.17 (m, 1H), 3.35 (bs, 1H), 3.48 (dd, 1H, J ¼ 11:5 and
11.0 Hz), 3.56 (dd, 1H, J ¼ 1:5 and 10.0 Hz), 3.68 (dd, 1H, J ¼
11:5 and 5.1 Hz), 3.73 (dd, 1H, J ¼ 3:4 and 9.5 Hz), 3.92 (dd,
1H, J ¼ 3:7 and 9.5 Hz), 3.97 (m, 1H), 4.28–4.44 (m, 2H), 4.52
(s, 2H), 4.70 (m, 1H), 4.97 (m, 1H), 5.03 (bd, 1H, J ¼ 7:6 Hz),
6.87 (bd, 1H, J ¼ 6:8 Hz), 7.18–7.40 (m, 6H); 13C NMR (CDCl3,
75 MHz) ꢁ 9.1, 12.1, 14.1, 17.6, 18.5, 18.8, 19.3, 22.7, 24.7,
28.3, 29.35, 29.44, 29.5, 29.6, 31.1, 31.9, 36.8, 53.3, 57.8, 60.2,
66.2, 67.1, 69.1, 73.4, 74.4, 78.9, 80.3, 98.0, 127.8, 127.8,
128.4, 137.3, 156.0, 169.8, 170.9, 172.4; FAB-HRMS Calcd for
C47H82N3O10 ðM þ HÞþ: 848.6001, Found m=z 848.6017. Found:
C, 66.59; H, 9.57; N, 5.10%. Calcd for C47H81N3O10: C, 66.56; H,
9.63; N, 4.95%.
WSC HCl (1.60 g, 10.3 mmol), and HOBt (2.79 g, 20.6 mmol),
ꢂ
and the mixture was stirred at room temperature for 20 h. The re-
action mixture was diluted with EtOAc, and washed successively
with a 1 M aqueous citric acid solution, a saturated aqueous
NaHCO3 solution and brine, and then dried. Removal of the sol-
vent left a residue, which was purified by column chromatography
(silica gel, 35 g, EtOAc/hexane = 1/8 as eluent) to afford the title
compound (992 mg, 72%) as an amorphous solid: Rf ¼ 0:25
22
(EtOAc/hexane = 1/3); ½ꢀꢁD ꢄ9 (c 1.6, CHCl3); IR (neat)
3310, 1740, 1710, 1650 cmꢄ1; 1H NMR (CDCl3, 300 MHz) ꢁ 0.91
and 0.96 (2d, each 3H, J ¼ 6:6 Hz), 1.20 (d, 3H, J ¼ 6:2 Hz), 1.43
(s, 9H), 2.10 (m, 1H), 4.00 (m, 1H), 4.18 (dq, 1H, J ¼ 2:2 and
6.2 Hz), 4.28 and 4.50 (2d, each 1H, J ¼ 11:9 Hz), 4.69 (dd, 1H,
J ¼ 2:2 and 9.2 Hz), 5.07 (d, 2H, J ¼ 11:9 Hz), 5.10 (m, 2H),
6.45 (d, 1H, J ¼ 9:2 Hz), 7.21–7.37 (m, 10H); 13C NMR (CDCl3,
75 MHz) ꢁ 16.1, 17.6, 19.1, 28.2, 31.1, 56.6, 59.7, 67.1, 70.7, 74.1,
79.6, 127.6, 127.6, 128.2, 128.3, 128.4, 128.4, 135.1, 137.6, 155.6,
170.0, 171.6; FAB-HRMS Calcd for C28H39N2O6 ðM þ HÞþ:
499.2808, Found m=z 499.2834. Found: C, 67.05; H, 7.61; N,
5.58%. Calcd for C28H38N2O6: C, 67.45; H, 7.68; N, 5.62%.
Boc–Val–Thr (25). A mixture of Boc–Val–Thr(Bzl)–OBzl
(85 mg, 0.17 mmol) and 10% Pd on carbon (32 mg) in EtOH
(2 mL) was stirred under an atmospheric pressure of H2 at room
temperature for 4 h. The insoluble material was removed by filtra-
tion and the filtrate was concentrated to give 25 (39 mg, 72%) as
an amorphous solid. This compound was used for the next reac-
tion without further purification: Rf ¼ 0:47 (MeOH/CHCl3 =
Further elution gave 26 (22.9 mg, 80%) as a colorless syrup:
22
Rf ¼ 0:45 (acetone/toluene = 1/4); ½ꢀꢁD þ2:3 (c 1.2, CHCl3);
IR (neat) 3290, 1740, 1710, 1640 cmꢄ1 1H NMR (CDCl3, 300
;
MHz) ꢁ 0.67 (d, 3H, J ¼ 6:6 Hz), 0.88 (t, 3H, J ¼ 6:9 Hz), 0.89
(d, 3H, J ¼ 6:6 Hz), 0.89 and 0.93 (2d, each 3H, J ¼ 6:7 Hz), 1.18
(d, 3H, J ¼ 6:6 Hz), 1.21–1.60 (m, 24H), 1.33 and 1.37 (2s, each
3H), 1.44 (s, 9H), 1.78–1.87 (m, 2H), 2.12 (m, 1H), 3.29 (bs, 1H),
3.48 (dd, 1H, J ¼ 11:2 and 11.2 Hz), 3.57 (dd, 1H, J ¼ 1:7 and
11.2 Hz), 3.67 (dd, 1H, J ¼ 3:6 and 9.4 Hz), 3.68 (m, 1H), 3.92
(dd, 1H, J ¼ 3:3 and 9.4 Hz), 3.96 (m, 1H), 4.33 (m, 1H), 4.45
(dd, 1H, J ¼ 2:8 and 7.4 Hz), 4.50 (s, 2H), 4.69 (ddd, 1H, J ¼ 3:3,
3.6, and 8.3 Hz), 4.98–5.05 (m, 2H), 6.82 (bd, 1H, J ¼ 7:4 Hz),
7.19 (bd, 1H, J ¼ 8:3 Hz), 7.24–7.38 (m, 5H); 13C NMR (CDCl3,
75 MHz) ꢁ 8.6, 12.2, 14.1, 17.6, 18.0, 18.7, 19.2, 22.7, 24.9, 28.3,
29.3, 29.4, 29.5, 29.59, 29.62, 30.5, 30.8, 31.4, 31.9, 36.8, 52.9,
56.9, 60.0, 66.1, 68.9, 69.5, 73.4, 75.1, 78.8, 80.0, 97.9, 127.0,
127.6, 127.8, 128.4, 129.5, 137.3, 155.8, 169.6, 170.3, 172.2;
FAB-HRMS Calcd for C47H82N3O10 ðM þ HÞþ: 848.6001, Found
m=z 848.6011. Found: C, 66.55; H, 9.59; N, 5.08%. Calcd for
C47H81N3O10: C, 66.56; H, 9.63; N, 4.95%.
N-[(1,1-Dimethylethoxy)carbonyl]-L-valyl-L-threonyl-O-(phen-
ylmethyl)-L-serine (1R)-1-[(1R,2S,3S)-2,4-Dihydroxy-1,3-de-
methylbutyl]tetradecyl Ester (28). A solution of the acetonide
26 (55 mg, 0.065 mmol) in acetic acid (3.5 mL) and H2O (1.5 mL)
was stirred at room temperature for 10 h. The reaction mixture was
diluted with H2O, and to this solution was added solid NaHCO3
(6.8 g) at 0 ꢃC. The products were extracted with EtOAc, and
the organic layer was washed with a saturated aqueous NaHCO3
22
1/2); ½ꢀꢁD ꢄ2:5 (c 1.1, MeOH); 1H NMR (MeOH-d4, 300 MHz)
ꢁ 0.94 and 0.98 (2d, each 3H, J ¼ 6:8 Hz), 1.18 (d, 3H, J ¼ 6:3
Hz), 1.45 (s, 9H), 2.08 (dqq, 1H, J ¼ 3:4, 6.8, and 6.8 Hz), 3.94
(bd, 1H, J ¼ 3:4 Hz), 4.30 (dq, 1H, J ¼ 2:9 and 6.3 Hz), 4.42
(bd, 1H, J ¼ 2:9 Hz); 13C NMR (MeOH-d4, 75 MHz) ꢁ 18.6, 19.8,
20.4, 28.7, 31.7, 58.9, 61.7, 68.6, 80.6, 158.0, 173.4, 174.8; FAB-
HRMS Calcd for C14H27N2O6 ðM þ HÞþ: 319.1869, Found m=z
319.1849.
N-[(1,1-Dimethylethoxy)carbonyl]-L-valyl-L-threonyl-O-(phen-
ylmethyl)-L-serine (1R)-1-[(1S)-1-[(4S,5S)-2,2,5-Trimethyl-1,3-
dioxan-4-yl]ethyl]tetradecyl Ester (26) and Its D-Serine Isomer

K. Kurosawa et al.
Bull. Chem. Soc. Jpn. Vol. 79, No. 6 (2006)
931
solution and brine, and then dried. Removal of the solvent left a
residue, which was purified by column chromatography (silica
gel, 1 g, acetone/toluene = 1/4 as eluent) to afford 28 (50 mg,
94%) as a colorless syrup: Rf ¼ 0:40 (acetone/toluene = 1/2);
sively with a 1 M aqueous citric acid solution, a saturated aqueous
NaHCO3 solution and brine, and then dried. Removal of the sol-
vent left a residue, which was purified by column chromatography
(silica gel, 1 g, acetone/toluene = 1/6 as eluent) to afford 30
(16.7 mg, 41% from 29) as a colorless syrup: Rf ¼ 0:53 (ace-
22
½ꢀꢁD ꢄ10 (c 0.75, CHCl3); IR (neat) 3300, 1740, 1700, 1630
21
cmꢄ1
;
1H NMR (CDCl3, 300 MHz) ꢁ 0.79 (d, 3H, J ¼ 7:1 Hz),
tone/toluene = 1/1); ½ꢀꢁD ꢄ33 (c 0.8, CHCl3); IR (neat) 3310,
1
0.87 (t, 3H, J ¼ 7:1 Hz), 0.90 and 0.92 (2d, each 3H, J ¼ 6:6 Hz),
0.93 (d, 3H, J ¼ 6:6 Hz), 1.16 (d, 3H, J ¼ 6:6 Hz), 1.21–1.35 (m,
22H), 1.44 (s, 9H), 1.55 (m, 1H), 1.80 (m, 4H), 2.13 (m, 1H),
3.25–3.60 (m, 5H), 3.69 (dd, 1H, J ¼ 3:7 and 9.4 Hz), 3.89 (dd,
1H, J ¼ 3:9 and 9.4 Hz), 3.99 (dd, 1H, J ¼ 5:4 and 8.1 Hz), 4.33
(m, 1H), 4.46 (dd, 1H, J ¼ 1:7 and 7.6 Hz), 4.51 (s, 2H), 4.65
(ddd, 1H, J ¼ 3:7, 3.9, and 7.8 Hz), 5.06 (m, 1H), 5.13 (d, 1H,
J ¼ 8:1 Hz), 6.99 (bd, 1H, J ¼ 7:6 Hz), 7.25–7.37 (m, 5H), 7.48
(bd, 1H, J ¼ 7:8 Hz); 13C NMR (CDCl3, 75 MHz) ꢁ 7.3, 14.0,
14.1, 17.7, 18.2, 19.3, 22.7, 25.5, 28.3, 29.3, 29.5, 29.6, 29.7,
30.7, 31.9, 32.0, 37.9, 38.3, 53.2, 57.2, 60.1, 66.7, 67.8, 69.3,
73.4, 78.4, 79.6, 80.2, 127.7, 127.9, 128.4, 137.1, 156.0, 169.9,
170.7, 172.4; FAB-HRMS Calcd for C44H78N3O10 ðM þ HÞþ:
808.5688, Found m=z 808.5697.
1730, 1650 cmꢄ1; H NMR (CDCl3, 300 MHz) ꢁ 0.89 (t, 3H, J ¼
6:8 Hz), 0.98 (d, 3H, J ¼ 7:2 Hz), 0.99 and 1.04 (2d, each 3H, J ¼
6:6 Hz), 1.12 (d, 3H, J ¼ 6:6 Hz), 1.18 (d, 3H, J ¼ 7:4 Hz), 1.21–
1.33 (m, 22H), 1.51 (m, 1H), 1.63 (m, 1H), 1.80 (m, 1H), 2.06 (m,
1H), 2.52 (m, 1H), 3.26 and 3.33 (2bs, each 1H), 3.57 (dd, 1H,
J ¼ 4:3 and 8.4 Hz), 3.89 (dd, 1H, J ¼ 6:3 and 9.9 Hz), 4.00 (dd,
1H, J ¼ 4:7 and 9.9 Hz), 4.12 (dd, 1H, J ¼ 7:4 and 9.0 Hz), 4.35–
4.45 (m, 2H), 4.49 (m, 1H), 4.50 and 4.58 (2d, each 1H, J ¼ 11:1
Hz), 4.90 (m, 1H), 6.80 (bd, 1H, J ¼ 7:1 Hz), 7.19 (bd, 1H, J ¼
7:4 Hz), 7.24–7.35 (m, 5H), 7.54 (bd, 1H, J ¼ 7:7 Hz); 13C NMR
(CDCl3, 75 MHz) ꢁ 14.1, 15.9, 16.0, 16.0, 16.2, 18.8, 19.2, 19.4,
22.7, 26.1, 29.4, 29.5, 29.6, 29.6, 30.2, 31.3, 31.9, 39.6, 45.8, 53.2,
58.0, 62.0, 65.2, 67.4, 69.2, 73.5, 79.9, 128.0, 128.5, 137.6, 169.6,
170.9, 172.7, 176.7; FAB-HRMS Calcd for C39H66N3O8
ðM þ HÞþ: 704.4850, Found m=z 704.4873.
N-[(1,1-Dimethylethoxy)carbonyl]-L-valyl-L-threonyl-O-(phen-
ylmethyl)-L-serine (1R)-1-[(1R,2R,3R)-3-Carboxy-2-hydroxy-
1-methylbutyl]tetradecyl Ester (29). To a solution of the triol
28 (47 mg, 0.058 mmol) in CH2Cl2 (9 mL) at 0 ꢃC were added
TEMPO (1.24 g Lꢄ1 solution in CH2Cl2; 0.073 mL), KBr (5.96
g Lꢄ1 solution in H2O; 0.115 mL), NaOCl (0.35 M solution in
H2O; 0.02 mL), and NaHCO3 (50 g Lꢄ1 solution in H2O; 0.02
mL). After being stirred at 0 ꢃC for 1 h, to the reaction mixture
was added a 20% aqueous Na2S2O3 solution. The products were
extracted with CHCl3, and the organic layer was washed with a
20% aqueous Na2S2O3 solution and then dried. Removal of the
solvent gave a crude aldehyde (47 mg), which was dissolved in
t-BuOH (3.7 mL) and H2O (0.9 mL). To this solution were added
Stevastelin B (1). A mixture of the macrocycle 30 (5.1 mg,
0.0073 mmol) and 20% Pd(OH)2 on carbon (6 mg) in MeOH
(1 mL) was stirred at room temperature under an atmospheric
pressure of H2 for 2 h. The insoluble material was removed by fil-
tration, and the filtrate was concentrated to give 31, which was
used in the next reaction without further purification: Rf ¼ 0:42
23
(MeOH/CHCl3 = 1/10); ½ꢀꢁD ꢄ51 (c 0.1, MeOH), IR (neat)
3350, 1740, and 1655 cmꢄ1 1H NMR (DMSO-d6, 300 MHz) ꢁ
;
0.74 (d, 3H, J ¼ 7:1 Hz), 0.83 (d, 3H, J ¼ 6:3 Hz), 0.86 (t, 3H,
J ¼ 6:6 Hz), 0.89 (d, 3H, J ¼ 6:8 Hz), 1.00 (d, 3H, J ¼ 6:3 Hz),
1.12 (d, 3H, J ¼ 7:3 Hz), 1.15–1.30 (m, 22H), 1.43 (m, 1H), 1.56
(m, 1H), 1.76 (m, 1H), 2.08 (ddq, 1H, J ¼ 6:3, 6.8, and 11.0 Hz),
2.18 (m, 1H), 3.50 (m, 1H), 3.61 (m, 1H), 3.69 (m, 1H), 3.99 (dd,
1H, J ¼ 10:3 and 11.0 Hz), 4.18 (ddq, 1H, J ¼ 2:2, 4.4, and 6.3
Hz), 4.27 (dd, 1H, J ¼ 9:8 and 2.2 Hz), 4.47 (m, 1H), 4.55 (m,
1H), 4.88 (m, 1H), 4.98 (d, 1H, J ¼ 4:4 Hz), 5.25 (d, 1H, J ¼
5:9 Hz), 7.64 (d, 1H, J ¼ 8:3 Hz), 7.87 (d, 1H, J ¼ 10:3 Hz), 8.31
(d, 1H, J ¼ 9:8 Hz); FAB-HRMS Calcd for C32H60N3O8 ðM þ
HÞþ: 614.4380 Found m=z 614.4408.
NaH2PO4 2H2O (36 mg, 0.23 mmol), HOSO2NH2 (28 mg, 0.29
ꢂ
mmol), and NaClO2 (31 mg, 0.35 mmol), and the mixture was stir-
red at room temperature for 1 h. To the reaction mixture at 0 ꢃC
was added a 1 M aqueous citric acid solution, and the products
were extracted with CHCl3. The organic layer was washed with
a 1 M aqueous citric acid solution and then dried. Removal of
the solvent gave 29 (47 mg, 100% crude yield) as a colorless syr-
up, which was used in the next reaction without further purifi-
To a solution of the crude alcohol 31 in pyridine (0.9 mL) at
0 ꢃC was added acetic anhydride (0.010 mL, 0.11 mmol), and the
mixture was stirred at 0 ꢃC for 2 h. To the reaction mixture was
added MeOH at 0 ꢃC, and the resulting mixture was concentrated
to give a residue, which was purified by column chromatography
(silica gel, 0.6 g, MeOH/CHCl3 = 1/60 as eluent) to afford 1
23
cation: Rf ¼ 0:31 (MeOH/CHCl3 = 1/10); ½ꢀꢁD ꢄ5 (c 0.76,
CHCl3); IR (neat) 3310, 1735, 1715, 1650 cmꢄ1
;
1H NMR
(CDCl3, 300 MHz) ꢁ 0.87 (t, 3H, J ¼ 6:3 Hz), 0.89 (d, 3H, J ¼
6:3 Hz), 0.96 (d, 3H, J ¼ 7:3 Hz), 0.96 (d, 3H, J ¼ 7:3 Hz), 1.10–
1.35 (m, 28H), 1.43 (s, 9H), 1.57 (m, 2H), 1.91 (m, 1H), 2.10 (m,
1H), 2.68 (m, 1H), 3.65 (m, 1H), 3.72 (m, 1H), 3.88 (m, 1H), 4.04
21
(3.2 mg, 67% from 30) as an amorphous solid: ½ꢀꢁD ꢄ51 (c
17
(dd, 1H, J ¼ 5:9 and 8.3 Hz), 4.32 (m, 1H), 4.46–4.51 (m, 3H),
0.25, CHCl3), {natural stevastelin B, ½ꢀꢁD ꢄ48 (c 0.1, CHCl3)
ꢀ;ꢂ
1
4.68 (m, 1H), 5.06 (m, 1H), 5.24 (bd, 1H, J ¼ 8:3 Hz), 7.26–7.35
(m, 6H), 7.42 (bd, 1H, J ¼ 8:3 Hz); FAB-HRMS Calcd for
C44H76N3O11 ðM þ HÞþ: 822.5480, Found m=z 822.5486.
(measured in our laboratory)}; H NMR (DMSO-d6, 300 MHz) ꢁ
0.73 (d, 3H, J ¼ 7:1 Hz, 4-Me), 0.82 (d, 3H, J ¼ 6:1 Hz, val-Me),
0.85 (t, 3H, J ¼ 6:3 Hz, –(CH2)11CH3), 0.88 (d, 3H, J ¼ 6:6 Hz,
val-Me), 1.00 (d, 3H, J ¼ 6:1 Hz, thr-Me), 1.13 (d, 3H, J ¼ 7:6
Hz, 2-Me), 1.23 (m, 22H, –(CH2)11CH3), 1.43 and 1.53 (2m, each
1H, H-6 and H-60), 1.72 (m, 1H, H-4), 1.98 (s, 3H, OAc), 2.10 (m,
1H, val-ꢂH), 2.19 (m, 1H, H-2), 3.61 (m, 1H, H-3), 3.94 (dd, 1H,
J ¼ 7:1 and 10.7 Hz, ser-ꢂH), 3.98 (dd, 1H, J ¼ 10:3 and 11.0 Hz,
val-ꢀH), 4.18 (m, 1H, thr-ꢂH), 4.27 (bd, 1H, J ¼ 9:1 Hz, thr-ꢀH),
4.40 (dd, 1H, J ¼ 6:6 and 10.7 Hz, ser-ꢂ0H), 4.73 (ddd, 1H, J ¼
6:6, 7.1, and 8.1 Hz, ser-ꢀH), 4.90 (d, 1H, J ¼ 4:4 Hz, thr-OH),
4.92 (m, 1H, H-5), 5.52 (d, 1H, J ¼ 5:1 Hz, 3-OH), 7.81 (d, 1H,
J ¼ 8:1 Hz, ser-NH), 7.93 (d, 1H, J ¼ 10:3 Hz, val-NH), 8.32
(d, 1H, J ¼ 9:1 Hz, thr-NH); 13C NMR (CDCl3, 75 MHz) ꢁ 6.5
N-[(2R,3R,4R,5R)-3,5-Dihydroxy-2,4-dimethyl-1-oxoocta-
decyl]-L-valyl-L-threonyl-O-(phenylmethyl)-L-serine (3!15)-
Lactone (30). To a solution of the carboxylic acid 29 (47 mg,
0.058 mmol) in CH2Cl2 (6 mL) under Ar at 0 ꢃC was added TFA
(1.1 mL). After being stirred at 0 ꢃC for 1 h, the reaction mixture
was concentrated and dried in vacuo to give 5 TFA, which was
ꢂ
dissolved in DMF (58 mL). To this solution under Ar at 0 ꢃC were
added diethylphosphoryl cyanide (DEPC, 0.0431 mL, 0.288
mmol) and Et3N (0.0445 mL, 0.317 mmol), and the mixture was
stirred at 0 ꢃC for 30 min, then at room temperature for 16 h.
The reaction mixture was diluted with EtOAc and washed succes-

932 Bull. Chem. Soc. Jpn. Vol. 79, No. 6 (2006)
Total Synthesis of Stevastelins
(4-CH3), 13.9 (18-C), 16.4 (2-CH3), 19.0 (val-CH3), 19.4 (val-
CH3), 20.5 (thr-CH3), 20.6 (COCH3), 22.1, 25.4, 28.69, 28.73,
28.9, 28.99, 29.04, 29.8 and 31.3 (7–17-C, val-ꢂC), 31.7 (6-C),
40.0 (4-C), 46.3 (2-C), 49.9 (ser-ꢀC), 57.7 (thr-ꢀC), 61.2 (val-
ꢀC), 62.4 (ser-ꢂC), 66.8 (thr-ꢂC), 75.3 (3-C), 78.8 (5-C), 169.4,
170.1, 170.4, 171.3 and 174.9 (ser-CO, thr-CO, val-CO, 1-C,
OCOCH3); 1H NMR (CDCl3, 300 MHz) ꢁ 0.88 (t, 3H, J ¼ 6:6 Hz,
–(CH2)11CH3), 1.03 (d, 3H, J ¼ 6:3 Hz, 4-Me), 1.05 (d, 6H, J ¼
6:6 Hz, val-Me2), 1.14 (d, 3H, J ¼ 6:3 Hz, thr-Me), 1.25 (m, 22H,
–(CH2)11CH3), 1.31 (d, 3H, J ¼ 7:4 Hz, 2-Me), 1.40–1.78 (m, 2H,
H-6 and H-60), 1.84 (m, 1H, H-4), 2.06 (s, 3H, OAc), 2.13 (m, 1H,
val-ꢂH), 2.66 (m, 1H, H-2), 2.97 and 3.39 (2bs, each 1H, 2 ꢅ
OH), 3.64 (m, 1H, H-3), 3.97 (dd, 1H, J ¼ 6:9 and 6.9 Hz, val-
ꢀH), 4.21 (m, 1H, ser-ꢀH), 4.44 (m, 1H, thr-ꢂH) 4.48 (m, 1H,
thr-ꢀH), 4.49 (dd, 1H, J ¼ 5:5 and 11.3 Hz, ser-ꢂH), 4.65 (dd,
1H, J ¼ 7:2 and 11.3 Hz, ser-ꢂ0H), 4.86 (m, 1H, H-5), 6.71 (bs,
1H, thr-NH), 7.20 (bs, 1H, val-NH), 7.51 (bs, 1H, ser-NH);
FAB-HRMS Calcd for C34H62N3O9 ðM þ HÞþ: 656.4486, Found
m=z 656.4477. The 1H and 13C NMR data were fully identical with
those of natural stevastelin B.2
(188 mg, 0.448 mmol) in CH2Cl2 (5.7 mL) at 0 ꢃC were added
chlorotriethylsilane (TESCl, 0.180 mL, 1.07 mmol) and Et3N
(0.378 mL, 2.69 mmol), and the mixture was stirred at room tem-
perature for 1 h. To the reaction mixture was added H2O at 0 ꢃC,
and the products were extracted with CHCl3. The organic layer
was washed with brine, and then dried. Removal of the solvent left
a residue, which was purified by column chromatography (silica
gel, 7 g, EtOAc/hexane = 1/19 as eluent) to afford 33 (236 mg,
21
98%) as a colorless syrup; ½ꢀꢁD ꢄ10 (c 0.5, CHCl3); IR (neat)
3500 cmꢄ1
;
1H NMR (CDCl3, 300 MHz) ꢁ 0.62 (q, 6H, J ¼ 7:9
Hz), 0.79 (d, 3H, J ¼ 6:8 Hz), 0.88 (t, 3H, J ¼ 6:6 Hz), 0.98 (t,
9H, J ¼ 7:9 Hz), 0.99 (d, 3H, J ¼ 6:8 Hz), 1.17–1.40 (m, 22H),
1.66 (m, 2H), 1.72–1.86 (m, 2H), 3.51 (m, 1H), 3.58 (m, 1H), 3.68
(m, 2H), 4.03 (d, 1H, J < 1 Hz), 4.45 and 4.61 (2d, each 1H,
J ¼ 11:2 Hz), 7.25–7.38 (m, 5H); 13C NMR (CDCl3, 75 MHz) ꢁ
4.2, 6.7, 7.6, 13.2, 14.1, 22.7, 25.1, 29.4, 29.6, 29.7, 30.0, 30.5,
31.9, 37.6, 37.9, 67.8, 71.7, 77.4, 83.4, 127.5, 127.8, 128.4,
138.7; FAB-HRMS Calcd for C33H63O3Si ðM þ HÞþ: 535.4547,
Found m=z 535.4545. Found: C, 73.97; H, 11.43%. Calcd for
C33H62O3Si: C, 74.09; H, 11.68%.
(2S,3S,4R,5R)-2,4-Dimethyl-5-(phenylmethoxy)-1,3-octadec-
anediol (32). To a solution of the alcohol 23 (169 mg, 0.456
mmol) in THF (13 mL) at 0 ꢃC under Ar were added potassium
bis(trimethylsilyl)amide (KHMDS, 0.5 M solution in toluene,
2.73 mL, 1.37 mmol) and BzlBr (0.081 mL, 0.68 mmol), and the
mixture was stirred at 0 ꢃC for 10 min. To the reaction mixture
was added a saturated aqueous NH4Cl solution at 0 ꢃC, and the
products were extracted with EtOAc. The organic layer was wash-
ed successively with a saturated aqueous NH4Cl solution, a satu-
rated aqueous NaHCO3 solution and brine, and then dried. Re-
moval of the solvent gave a crude benzyl ether (210 mg), which
was used in the next reaction without further purification. A part
of this compound was purified by column chromatography and
An Inseparable Mixture of (3S,6S,7S)-10,10-Diethyl-7-
methyl-6-[(1S,2R)-1-methyl-2-(phenylmethoxy)pentadecyl]-4-
oxo-3-[(phenylmethoxy)methyl]-5,9-dioxa-2-aza-10-siladodeca-
noic Acid Phenylmethyl Ester (34) and Its (3R)-Isomer. To a
solution of the alcohol 33 (73 mg, 0.14 mmol), Cbz–Ser(Bzl) (179
mg, 0.54 mmol) and DMAP (50 mg, 0.41 mmol) in THF (7.3 mL)
under Ar at 0 ꢃC were added 2,4,6-trichlorobenzoyl chloride (0.11
mL, 0.68 mmol) and Et3N (0.096 mL, 0.68 mmol). After being
stirred at 0 ꢃC for 1.5 h, to the reaction mixture was added a satu-
rated aqueous NH4Cl solution at 0 ꢃC. The products were extract-
ed with EtOAc and the organic layer was washed successively
with a saturated aqueous NH4Cl solution, a saturated aqueous
NaHCO3 solution and brine, and then dried. Removal of the sol-
vent left a residue, which was purified by column chromatography
(silica gel, 10 g, EtOAc/hexane = 1/30 as eluent) to afford a mix-
ture (ca. 1:1) of 34 and its (3R)-isomer (89 mg, 77%) as a colorless
27
used as an analytical sample: ½ꢀꢁD þ21 (c 1.4, CHCl3); 1H NMR
(CDCl3, 300 MHz) ꢁ 0.70 (d, 3H, J ¼ 6:6 Hz), 0.88 (t, 3H, J ¼
6:8 Hz), 1.00 (d, 3H, J ¼ 6:8 Hz), 1.15–1.73 (m, 24H), 1.35 and
1.42 (2s, each 3H), 1.88 (m, 2H), 3.33 (m, 1H), 3.51 (dd, 1H, J ¼
11:5 and 11.2 Hz), 3.61 (dd, 1H, J ¼ 10:3 and 1.5 Hz), 3.70
(dd, 1H, J ¼ 11:5 and 4.9 Hz), 4.50 (s, 2H), 7.22–7.39 (m, 5H);
13C NMR (CDCl3, 75 MHz) ꢁ 9.7, 12.3, 14.1, 18.9, 22.7, 24.7,
29.4, 29.6, 29.6, 29.7, 29.7, 29.9, 30.6, 30.7, 31.9, 36.6, 66.4,
72.1, 74.1, 81.9, 97.8, 127.3, 127.8, 128.3, 139.8; FAB-HRMS
Calcd for C30H53O3 ðM þ HÞþ: 461.3995, Found m=z 461.3976.
Found: C, 78.09; H, 11.29%. Calcd for C30H52O3: C, 78.21; H,
11.38%.
1
syrup; IR (neat) 3500–3250, 1730, 1710 cmꢄ1; H NMR (CDCl3,
300 MHz) ꢁ 0.56 (q, 3H, J ¼ 7:8 Hz), 0.56 (q, 3H, J ¼ 8:1 Hz),
0.90 (m, 18H), 1.20–1.35 (m, 22H), 1.61 (m, 2H), 2.01 (m, 2H),
3.22–3.38 (m, 2H), 3.60 (d, 0.5H, J ¼ 4:6 and 9.8 Hz), 3.61 (dd,
0.5H, J ¼ 5:4 and 9.8 Hz), 3.70 and 3.72 (2dd, each 0.5H, J ¼
3:2 and 9.5 Hz), 3.91 (dd, 1H, J ¼ 2:7 and 9.5 Hz), 4.29 and 4.36
(2d, each 1H, J ¼ 11:5 Hz), 4.44 (d, 1H, J ¼ 11:2 Hz), 4.51 (m,
2H), 5.10 (m, 3H), 5.62 and 5.64 (2d, each 0.5H, J ¼ 8:1 Hz),
7.20–7.40 (m, 15H); FAB-HRMS Calcd for C51H80NO7Si ðM þ
HÞþ: 846.5704, Found m=z 846.5721. Found: C, 72.12; H, 9.24;
N, 1.50%. Calcd for C51H79NO7Si: C, 72.38; H, 9.41; N, 1.66%.
An Inseparable Mixture of N-[(1,1-Dimethylethoxy)carbon-
yl]-L-valyl-L-threonyl-O-(phenylmethyl)-L-serine (1S,2S,3R)-2-
Methyl-1-[(1S)-1-methyl-2-[(triethylsilyl)oxy]ethyl]-3-(phenyl-
A solution of the crude benzyl ether (210 mg, 0.456 mmol) in
acetic acid (25.2 mL) and H2O (6.3 mL) was stirred at room tem-
perature for 14 h. Removal of the solvent left a residue, which was
purified by column chromatography (silica gel, 5 g, EtOAc/hex-
ane = 1/2 as eluent) to afford 32 (188 mg, 98% from 23) as a col-
27
orless syrup; ½ꢀꢁD ꢄ44 (c 1.1, CHCl3); IR (neat) 3400 cmꢄ1
;
methoxy)hexadecyl Ester (35) and Its D-Serine Isomer.
A
1H NMR (CDCl3, 300 MHz) ꢁ 0.74 (d, 3H, J ¼ 6:8 Hz), 0.88 (t,
3H, J ¼ 6:6 Hz), 0.95 (d, 3H, J ¼ 7:1 Hz), 1.15–1.35 (m, 22H),
1.42–1.95 (m, 4H), 3.50–3.75 (m, 5H), 4.11 (bs, 1H), 4.42 (d,
1H, J ¼ 11:2 Hz), 4.68 (d, 1H, J ¼ 11:2 Hz), 7.25–7.40 (m, 5H);
13C NMR (CDCl3, 75 MHz) ꢁ 5.1, 13.6, 14.1, 22.7, 25.7, 29.4,
29.5, 29.6, 29.6, 29.7, 29.8, 30.3, 31.9, 36.2, 37.5, 69.0, 70.9,
82.9, 85.5, 127.8, 127.9, 128.6, 139.8; FAB-HRMS Calcd for
C27H49O3 ðM þ HÞþ: 421.3682, Found m=z 421.3690. Found: C,
76.85; H, 11.15%. Calcd for C27H48O3: C, 77.09; H, 11.50%.
(2S,3S,4R,5R)-2,4-Dimethyl-5-(phenylmethoxy)-1-[(triethyl-
silyl)oxy]-3-octadecanol (33). To a solution of the alcohol 32
mixture of 34 and its D-serine isomer (25 mg, 0.029 mmol) in
MeOH (2.5 mL) was stirred in the presence of 10% Pd on a carbon
ethylenediamine complex (21 mg) under an atmospheric pressure
of H2 at room temperature for 1 h. The insoluble material was re-
moved by filtration, and the filtrate was concentrated to give a
crude amine, which was dissolved in DMF (3.4 mL). To this solu-
tion at 0 ꢃC were added the dipeptide 25 (14 mg, 0.044 mmol),
WSC HCl (13 mg, 0.070 mmol), and HOBt (9.5 mg, 0.070 mmol),
ꢂ
and the whole mixture was stirred at room temperature for 2 h.
The reaction mixture was diluted with EtOAc and washed succes-
sively with a saturated aqueous NH4Cl solution, a saturated aque-

K. Kurosawa et al.
Bull. Chem. Soc. Jpn. Vol. 79, No. 6 (2006)
933
ous NaHCO3 solution and brine, and then dried. Removal of the
solvent left a residue, which was purified by column chromatogra-
phy (silica gel, 1 g, acetone/toluene = 1/20 as eluent) to afford a
mixture (ca. 1:1) of 35 and its epimer (27.8 mg, 94%) as a color-
less syrup; 1H NMR (CDCl3, 300 MHz) ꢁ 0.55 (q, 3H, J ¼ 7:8
Hz), 0.56 (q, 3H, J ¼ 7:8 Hz), 0.88–1.00 (m, 24H), 1.16 (d, 1.5H,
J ¼ 6:3 Hz), 1.17 (d, 1.5H, J ¼ 6:2 Hz), 1.20–1.35 (m, 22H), 1.44
(s, 9H), 1.57 (m, 2H), 1.88–2.25 (m, 3H), 3.22–3.35 (m, 2H), 3.43
(bs, 1H), 3.59 (dd, 1H, J ¼ 9:8 and 4.6 Hz), 3.67 (dd, 0.5H, J ¼
9:8 and 3.7 Hz), 3.71 (dd, 0.5H, J ¼ 9:8 and 3.7 Hz), 3.88 (dd,
1H, J ¼ 9:8 and 3.7 Hz), 3.96 (m, 1H), 4.25–4.58 (m, 6H), 4.66
(m, 1H), 4.98–5.10 (m, 2H), 6.86 (bd, 0.5H, J ¼ 7:3 Hz), 6.90
(bd, 0.5H, J ¼ 7:3 Hz), 7.15–7.40 (m, 11H); MS (FAB) m=z
1013 (M þ H).
127.5, 127.7, 127.7, 127.9, 128.3, 128.5, 137.1, 138.7, 155.9,
170.4, 170.8, 172.4; FAB-HRMS Calcd for C51H84N3O10 ðM þ
HÞþ: 898.6157, Found m=z 898.6154. Found: C, 68.21; H, 9.38;
N, 4.47%. Calcd for C51H83N3O10: C, 68.20; H, 9.31; N, 4.68%.
Cyclo[(2R,3R,4S,5R)-3-hydroxy-2,4-dimethyl-5-(phenylmeth-
oxy)octadecanoyl-L-valyl-L-threonyl-O-(phenylmethyl)-L-seryl]
(39). To a solution of the diol 36 (9.3 mg, 0.010 mmol) in CH2Cl2
(1.7 mL) at 0 ꢃC were added TEMPO (1.24 g Lꢄ1 solution in
CH2Cl2; 0.013 mL), KBr (5.96 g Lꢄ1 solution in H2O; 0.021 mL),
NaOCl (0.35 M solution in H2O; 0.036 mL), and NaHCO3 (50
g Lꢄ1 solution in H2O; 0.036 mL). After being stirred at 0 ꢃC for
1.5 h, to the reaction mixture was added a 20% aqueous Na2S2O3
solution. The products were extracted with CHCl3, and the organ-
ic layer was washed with a 20% aqueous Na2S2O3 solution, and
then dried. Removal of the solvent gave a crude aldehyde (9.3
mg), which was dissolved in t-BuOH (1.49 mL) and H2O (0.37
N-[(1,1-Dimethylethoxy)carbonyl]-L-valyl-L-threonyl-O-(phen-
ylmethyl)-L-serine (1S,2S,3R)-1-[(1S)-2-Hydroxy-1-methylethyl]-
2-methyl-3-(phenylmethoxy)hexadecyl Ester (36) and Its D-
Serine Isomer (37). To a solution of a mixture (ca. 1:1) of the
O-TES ether 35 and its D-serine isomer (24 mg, 0.065 mmol) in
THF (1.0 mL) at 0 ꢃC were added acetic acid (1.0 mL) and H2O
(0.34 mL), and the mixture was stirred at 0 ꢃC for 1 h. The reaction
mixture was diluted with H2O, and to this solution was added sol-
id NaHCO3 (1.8 g) at 0 ꢃC. The products were extracted with
EtOAc, and the organic layer was washed with a saturated aque-
ous NaHCO3 solution and brine, and then dried. Removal of the
solvent left a residue, which was purified by column chromatogra-
phy (silica gel, 2 g, acetone/toluene = 1/8 as eluent) to first
mL). To this solution were added NaH2PO4 2H2O (6.5 mg,
ꢂ
0.041 mmol), HOSO2NH2 (5.0 mg, 0.052 mmol), and NaClO2
(5.6 mg, 0.062 mmol), and the mixture was stirred at 0 ꢃC for
20 min. To the reaction mixture at 0 ꢃC was added a 1 M aqueous
citric acid solution, and the products were extracted with CHCl3.
The organic layer was washed with a 1 M aqueous citric acid solu-
tion and then dried. Removal of the solvent gave the crude carbox-
ylic acid 38, which was dissolved in CH2Cl2 (1.4 mL). To this so-
lution under Ar at ꢄ18 ꢃC was added TFA (0.28 mL), and the mix-
ture was stirred at ꢄ18 ꢃC for 1 h. The reaction mixture was con-
centrated and dried in vacuo to give the crude amino carboxylic
23
afford 37 (9.0 mg, 43%) as a colorless syrup; ½ꢀꢁD ꢄ29 (c 1.6,
acid 6 TFA, which was dissolved in DMF (5.2 mL). To this solu-
ꢂ
CHCl3); IR (neat) 3300, 1730, 1715, 1650 cmꢄ1
;
1H NMR
tion under Ar at 0 ꢃC were added DEPC (0.0039 mL, 0.026 mmol)
and Et3N (0.0039 mL, 0.028 mmol), and the mixture was stirred at
0 ꢃC for 30 min, and then at room temperature for 14 h. The reac-
tion mixture was diluted with EtOAc and washed successively
with a 1 M aqueous HCl solution, a saturated aqueous NaHCO3
solution and brine, and then dried. Removal of the solvent left a
residue, which was purified by column chromatography (silica
gel, 1 g, acetone/toluene = 1/12 as eluent) to afford 39 (2.4 mg,
(CDCl3, 300 MHz) ꢁ 0.88 (t, 3H, J ¼ 6:8 Hz), 0.91 (d, 3H, J ¼
6:6 Hz), 0.91 (d, 3H, J ¼ 6:6 Hz), 0.96 (d, 3H, J ¼ 6:8 Hz), 0.96
(d, 3H, J ¼ 6:8 Hz), 1.16 (d, 3H, J ¼ 6:3 Hz), 1.19–1.35 (m, 22H),
1.44 (s, 9H), 1.38–1.67 (m, 2H), 1.84 (m, 1H), 2.02 (m, 1H), 2.18
(m, 1H), 2.46 (bs, 1H), 3.26 (m, 1H), 3.32–3.55 (m, 2H), 3.61 (bs,
1H), 3.67 (dd, 1H, J ¼ 3:7 and 9.5 Hz), 3.93 (dd, 1H, J ¼ 3:7 and
9.5 Hz), 3.98 (m, 1H), 4.37 (m, 2H), 4.37 (d, 1H, J ¼ 11:0 Hz),
4.48 (d, 1H, J ¼ 12:0 Hz), 4.50 (d, 1H, J ¼ 11:0 Hz), 4.53 (d, 1H,
J ¼ 12:0 Hz), 4.68 (ddd, 1H, J ¼ 3:7, 3.7, and 7.8 Hz), 5.02 (m,
1H), 5.07 (d, 1H, J ¼ 8:1 Hz), 7.03 (d, 1H, J ¼ 7:3 Hz), 7.18–
7.40 (m, 10H), 7.42 (d, 1H, J ¼ 7:8 Hz); 13C NMR (CDCl3, 75
MHz) ꢁ 10.2, 14.1, 14.3, 17.6, 18.6, 19.3, 22.6, 25.0, 28.2, 29.3,
29.6, 29.7, 29.8, 30.4, 31.9, 36.9, 37.1, 53.3, 57.7, 60.2, 63.6,
66.7, 69.1, 71.7, 73.5, 78.5, 80.3, 80.8, 127.5, 127.6, 127.7,
127.9, 128.3, 128.4, 137.0, 138.6, 156.1, 170.4, 170.9, 172.5;
FAB-HRMS Calcd for C51H84N3O10 ðM þ HÞþ: 898.6157, Found
m=z 898.6181. Found: C, 68.18; H, 9.43; N, 4.53%. Calcd for
C51H83N3O10: C, 68.20; H, 9.31; N, 4.68%.
25
29% from 36) as a colorless syrup; ½ꢀꢁD ꢄ39 (c 0.2, CHCl3); IR
1
(neat) 3450, 1740, 1670 cmꢄ1; H NMR (DMSO-d6, 300 MHz) ꢁ
0.59 (d, 3H, J ¼ 6:8 Hz, 4-Me), 0.85 (t, 3H, J ¼ 6:3 Hz, –(CH2)11-
CH3), 0.86 (d, 3H, J ¼ 5:9 Hz, val-Me), 0.92 (d, 3H, J ¼ 6:6 Hz,
val-Me), 0.98 (d, 3H, J ¼ 7:3 Hz, 2-Me), 1.07 (d, 3H, J ¼ 6:1 Hz,
thr-Me), 1.10–1.58 (m, 23H, –(CH2)11CH3 and H-6), 1.67 (m, 1H,
H-60), 1.87–2.12 (m, 2H, H-4 and val-ꢂH), 2.59 (m, 1H, H-2),
3.60 (dd, 1H, J ¼ 2:2 and 9.8 Hz, ser-ꢂH), 3.71 (m, 1H, H-5),
3.86 (dd, 1H, J ¼ 3:4 and 9.8 Hz, ser-ꢂ0H), 3.91–4.09 (m, 2H,
val-ꢀH and thr-ꢂH), 4.39 and 4.57 (2d, each 1H, J ¼ 11:7 Hz,
OCH2Ph), 4.43–4.65 (m, 2H, OCH2Ph), 4.80 (m, 1H, ser-ꢀH),
4.96 (m, 1H, H-3), 5.21 (d, 1H, J ¼ 4:6 Hz, thr-OH), 7.17–7.42
(m, 10H, Ph), 7.49 (d, 1H, J ¼ 10:0 Hz, val-NH), 7.81 (m, 2H,
thr-NH and ser-NH); 13C NMR (DMSO-d6, 75 MHz) ꢁ 9.7, 13.7,
14.0, 19.0, 19.2, 21.0, 22.1, 25.0, 28.7, 29.0, 29.2, 30.4, 31.3,
37.1, 41.5, 51.7, 59.4, 61.7, 65.3, 70.3, 72.6, 77.9, 78.9, 127.4,
127.5, 127.5, 127.7, 128.2, 138.1, 139.0, 169.5, 170.5, 170.9;
FAB-HRMS Calcd for C46H72N3O8 ðM þ HÞþ: 794.5320, Found
m=z 794.5298.
Macrocycle Possessing a Proposed Structure of Stevastelin
C3 (3). A mixture of the macrocycle 39 (2.5 mg, 0.0031 mmol)
and 10% Pd on carbon (4 mg) in MeOH (1 mL) was stirred at
room temperature under an atmospheric pressure of H2 for 3 h.
The insoluble material was removed by filtration, and the filtrate
was concentrated to give a residue, which was purified by column
chromatography (silica gel, 0.3 g, MeOH/CHCl3 = 1/30 as elu-
Further elution gave 36 (9.4 mg, 45%) as a colorless syrup;
23
½ꢀꢁD ꢄ27 (c 0.7, CHCl3); IR (neat) 3300, 1740, 1715, 1650
cmꢄ1
;
1H NMR (CDCl3, 300 MHz) ꢁ 0.88 (t, 3H, J ¼ 6:6 Hz),
0.89 (d, 3H, J ¼ 6:6 Hz), 0.93 (d, 3H, J ¼ 6:6 Hz), 0.93 (d, 3H,
J ¼ 6:6 Hz), 1.00 (d, 3H, J ¼ 6:3 Hz), 1.17 (d, 3H, J ¼ 6:3 Hz),
1.15–1.35 (m, 22H), 1.35–1.63 (m, 2H), 1.43 (s, 9H), 1.90 (m,
1H), 2.03 (m, 1H), 2.14 (m, 1H), 2.44 (bs, 1H), 3.21 (m, 1H),
3.35–3.57 (m, 3H), 3.66 (dd, 1H, J ¼ 3:2 and 9.5 Hz), 3.86 (dd,
1H, J ¼ 3:7 and 9.5 Hz), 3.97 (m, 1H), 4.32 (d, 1H, J ¼ 11:5 Hz),
4.34 (m, 1H), 4.44 (m, 1H), 4.45 (d, 1H, J ¼ 11:5 Hz), 4.48 (bs,
2H), 4.68 (ddd, 1H, J ¼ 3:2, 3.8, and 8.3 Hz), 4.96–5.13 (m, 2H),
6.97 (d, 1H, J ¼ 7:6 Hz), 7.20–7.42 (m, 10H), 7.37 (d, 1H, J ¼
8:3 Hz); 13C NMR (CDCl3, 75 MHz) ꢁ 10.1, 14.1, 14.2, 17.6, 18.2,
19.3, 22.7, 24.5, 28.3, 29.4, 29.6, 29.7, 29.9, 30.1, 30.6, 31.9, 37.1,
53.1, 56.9, 60.2, 63.9, 66.6, 69.3, 71.7, 73.4, 77.9, 80.2, 81.0,

934 Bull. Chem. Soc. Jpn. Vol. 79, No. 6 (2006)
Total Synthesis of Stevastelins
25
ent) to afford 3 (1.4 mg, 74%) as an amorphous solid; ½ꢀꢁD ꢄ55
(c 0.34, MeOH); 1H NMR (DMSO-d6, 300 MHz) ꢁ 0.52 (d, 3H,
J ¼ 6:9 Hz, 4-Me), 0.86 (t, 3H, J ¼ 6:9 Hz, –(CH2)12CH3), 0.88
(d, 3H, J ¼ 6:0 Hz, val-Me), 0.93 (d, 3H, J ¼ 6:6 Hz, val-Me),
1.07 (d, 3H, J ¼ 6:3 Hz, thr-Me), 1.09 (d, 3H, J ¼ 7:2 Hz, 2-Me),
1.14–1.41 (m, 24H, –(CH2)12CH3), 1.66 (m, 1H, H-4), 2.04 (m,
1H, val-ꢂH), 2.86 (m, 1H, H-2), 3.54 (m, 1H, ser-ꢂH), 3.85 (m,
1H, H-5), 3.92 (m, 1H, ser-ꢂH), 4.03 (m, 2H, val-ꢀH and thr-
ꢂH), 4.13 (dd, 1H, J ¼ 9:9 and 2.4 Hz, thr-ꢀH), 4.31 (d, 1H, J ¼
5:7 Hz, 5-OH), 4.60 (m, 1H, ser-ꢀH), 4.91 (m, 1H, H-3), 5.03 (dd,
1H, J ¼ 4:8 and 5.1 Hz, ser-OH), 5.14 (d, 1H, J ¼ 4:8 Hz, thr-
OH), 7.54 (d, 1H, J ¼ 9:9 Hz, val-NH), 7.84 (d, 1H, J ¼ 9:9 Hz,
ser-NH), 7.88 (d, 1H, J ¼ 9:0 Hz, thr-NH); 13C NMR (DMSO-
d6, 75 MHz) ꢁ 9.3, 13.7 and 14.0 (2-CH3, 4-CH3, 18-C), 19.0, 19.3
and 21.0 [val-(CH3)2, thr-CH3], 22.1, 25.8, 28.7, 28.9, 29.0,
29.1, 29.1, 29.2, 31.3 and 35.0 (6–17-C, val-ꢂC), 39.3 (4-C), 41.3
(2-C), 53.7 (ser-ꢀC), 59.5 (val-ꢀC), 60.9 (ser-ꢂC), 61.7 (thr-ꢀC),
65.3 (thr-ꢂC), 69.0 (5-C), 79.4 (3-C), 169.9, 170.4, 170.7 and
170.9 (ser-CO, thr-CO-, val-CO, 1-C); FAB-HRMS Calcd for
C32H60N3O8 ðM þ HÞþ: 614.4380, Found m=z 614.4407.
ꢀH), 5.24 (d, 1H, J ¼ 4:4 Hz, thr-OH), 7.50 (m, 1H, ser-NH),
7.67 (d, 1H, J ¼ 10:2 Hz, val-NH), 7.72 (d, 1H, J ¼ 9:0 Hz, thr-
NH); 13C NMR (75 MHz, DMSO-d6) ꢁ 9.2 (4-CH3), 13.8 (2-CH3),
13.9 (18-C), 19.0 (val-CH3), 19.2 (val-CH3), 20.7 (COCH3), 20.9
(thr-CH3), 22.1, 25.7, 28.7, 29.0, 29.1, 29.1, 31.3 and 34.9 (6–17-
C, val-ꢂC), 39.1 (4-C), 41.1 (2-C), 50.2 (ser-ꢀC), 59.4 (thr-ꢀC),
61.6 (val-ꢀC), 63.2 (ser-ꢂC), 65.2 (thr-ꢂC), 69.0 (5-C), 80.2 (3-
C), 168.7, 170.1, 170.5, 170.7 and 170.8 (ser-CO, thr-CO, val-
CO, 1-C, OCOCH3); FAB-HRMS Calcd for C34H62N3O9
ðM þ HÞþ: 656.4486, Found m=z 656.4494, {natural stevastelin
B3, Calcd for C34H62N3O9 ðM þ HÞþ: 656.4486, Found m=z
656.4490 (measured in our laboratory)}. The 1H and 13C NMR da-
ta were fully identical with those of natural stevastelin B3.
(4R,5S)-2,2,5-Trimethyl-4-[(1S)-1-methylpentadecyl]-1,3-di-
oxane (41). At 0 ꢃC, a THF (4 mL) solution of the alcohol 23
(123 mg, 0.332 mmol) was added dropwise to a suspension of
NaH (127 mg, 3.32 mmol, washed with hexane) in THF (1 mL),
and the mixture was stirred at room temperature for 3 h. To this
suspension were added CS2 (1.2 mL, 19.9 mmol) and MeI (0.414
mL, 6.65 mmol) at 0 ꢃC. After being stirred at room temperature
for 22 h, to the reaction mixture was added H2O at 0 ꢃC. The prod-
ucts were extracted with Et2O, the organic layer was washed with
H2O, and then dried. Removal of the solvent left a residue, which
was purified by column chromatography (silica gel, 3 g, EtOAc/
hexane = 1/30 as eluent) to afford the dithiocarbonate ester 40
Chiral HPLC Analysis of Amino Acids in Compound 3.
Compound 3 (0.5 mg) in aqueous HCl (6 M; 1 mL) was heated
to 110 ꢃC for 21 h in a sealed tube. Removal of the solvent left
a residue, which was dissolved in an aqueous CuSO4 (0.5 mM)
solution. The resulting solution was subjected to HPLC analysis
using a chiral column (MCI GEL CRS 10W, 4:6 ꢅ 50 mm,
Mitsubishi Chemical Industries Limited) at room temperature,
and the amino acids were detected by UV (254 nm). HPLC was
carried out with an aqueous CuSO4 (0.5 mM) solution as the mo-
bile phase at a flow rate of 1.0 mL minꢄ1 (condition A) or with an
aqueous CuSO4 (0.1 mM) solution at a flow rate of 0.5 mL minꢄ1
(condition B). Under condition A, the retention time of L-valine
was 8.1 min (D-valine 5.0 min). Under condition B, retention times
of L-serine and L-threonine were 8.2 and 8.9 min, respectively (D-
serine 7.0 min; D-threonine 7.3 min; D-allothreonine 11.2 min; and
L-allothreonine 14.5 min). These analyses revealed that the amino
acids in compound 3 were L-serine, L-valine, and L-threonine.
By similar experiments, the structures of the amino acids in nat-
ural stevastelins C3, B3, compounds 37, 46, and 47 were assigned.
For compounds 37, 46, and 47, de-O-benzyl products prepared by
hydrogenolysis (H2, 10% Pd/C in MeOH) were subjected to the
analyses.
21
(153 mg, 100%) as a yellow syrup; ½ꢀꢁD þ22 (c 0.6, CHCl3);
IR (neat) 1225, 1050 cmꢄ1 1H NMR (CDCl3, 300 MHz) ꢁ 0.70
;
(d, 3H, J ¼ 6:6 Hz), 0.88 (t, 3H, J ¼ 6:9 Hz), 0.98 (d, 3H, J ¼
7:2 Hz), 1.16–1.38 (m, 22H), 1.34 and 1.41 (2s, each 3H), 1.71
(m, 2H), 1.83 (dddq, 1H, J ¼ 11:1, 5.4, 10.2, and 6.6 Hz), 2.08
(m, 1H), 2.54 (s, 3H), 3.51 (dd, 1H, J ¼ 11:1 and 11.4 Hz), 3.62
(dd, 1H, J ¼ 10:2 and 1.5 Hz), 3.69 (dd, 1H, J ¼ 5:4 and 11.4
Hz), 5.80 (m, 1H, H-5); 13C NMR (CDCl3, 75 MHz) ꢁ 8.6, 12.3,
14.1, 18.5, 18.7, 22.7, 25.1, 29.3, 29.4, 29.5, 29.6, 29.6, 29.6,
29.7, 30.6, 31.1, 31.9, 36.8, 66.1, 75.3, 87.4, 98.0, 215.6; FAB-
HRMS Calcd for C25H49O3S2 ðM þ HÞþ: 461.3123, Found m=z
461.3118. Found: C, 65.37; H, 10.31%. Calcd for C25H48O3S2:
C, 65.17; H, 10.50%.
To a solution of the dithiocarbonate ester 40 (153 mg,
0.332 mmol) in toluene (6 mL) under Ar at 130 ꢃC were added a
solution of AIBN (818 mg, 4.99 mmol) and n-Bu3SnH (1.34 mL,
4.49 mmol) in toluene (17 mL) via a cannula. After being stirred
at 130 ꢃC for 7 h, the reaction mixture was concentrated to give
a residue, which was purified by column chromatography (silica
gel, 7 g, EtOAc/hexane = 1/40 as eluent) to afford 41 (110 mg,
Stevastelin B3 (2). To a solution of the alcohol 3 (3.0 mg,
0.0050 mmol) in pyridine (0.6 mL) at 0 ꢃC was added acetic anhy-
dride (0.22 M solution in pyridine; 0.023 mL). After being stirred
at room temperature for 5 h, to the reaction mixture was added
MeOH at 0 ꢃC. The resulting mixture was diluted with EtOAc
and washed successively with a 1 M aqueous HCl solution, a satu-
rated aqueous NaHCO3 solution and brine, and then dried. Re-
moval of the solvent left a residue, which was purified by column
chromatography (silica gel, 0.9 g, MeOH/CHCl3 = 1/100 as elu-
21
93% from 23) as a yellow syrup; ½ꢀꢁD þ22 (c 0.5, CHCl3);
1H NMR (CDCl3, 300 MHz) ꢁ 0.70 (d, 3H, J ¼ 6:8 Hz), 0.85 (d,
3H, J ¼ 6:6 Hz), 0.88 (t, 3H, J ¼ 6:3 Hz), 1.22–1.32 (m, 26H),
1.35 and 1.40 (2s, each 3H), 1.60 (m, 1H), 1.83 (dddq, 1H, J ¼
11:2, 4.9, 10.3, and 6.8 Hz), 3.42 (dd, 1H, J ¼ 10:3 and 2.0 Hz),
3.48 (dd, 1H, J ¼ 11:2 and 11.5 Hz), 3.69 (dd, 1H, J ¼ 11:5 and
4.9 Hz); 13C NMR (CDCl3, 75 MHz) ꢁ 12.3, 12.7, 14.1, 19.0, 22.7,
26.5, 27.4, 29.4, 29.6, 29.7, 29.8, 30.8, 31.9, 33.2, 33.6, 66.4, 76.7,
97.9; FAB-HRMS Calcd for C23H47O2 ðM þ HÞþ: 355.3576,
Found m=z 355.3596. Found: C, 77.92; H, 12.99%. Calcd for
C23H46O2: C, 77.90; H, 13.07%.
26
ent) to afford 2 (1.2 mg, 38%) as an amorphous solid; ½ꢀꢁD ꢄ53
25:5
(c 0.1, CHCl3), {natural stevastelin B3, ½ꢀꢁD
ꢄ51 (c 0.255,
1
CHCl3) (measured in our laboratory)}; H NMR (DMSO-d6, 300
MHz) ꢁ 0.54 (d, 3H, J ¼ 6:8 Hz, 4-Me), 0.85 (t, 3H, J ¼ 6:6 Hz,
–(CH2)12CH3), 0.90 (d, 3H, J ¼ 6:8 Hz, val-Me), 0.93 (d, 3H, J ¼
6:6 Hz, val-Me), 1.08 (d, 3H, J ¼ 6:1 Hz, thr-Me), 1.12 (d, 3H,
J ¼ 6:8 Hz, 2-Me), 1.17–1.35 (m, 24H, –(CH2)12CH3), 1.72 (m,
1H, H-4), 2.01 (s, 3H, OAc), 2.05 (m, 1H, val-ꢂH), 2.90 (m,
1H, H-2), 3.84 (m, 1H, H-5), 4.01 (m, 2H, val-ꢀH and thr-ꢂH),
4.13 (m, 1H, thr-ꢀH), 4.18 (m, 1H, ser-ꢂH), 4.35 (m, 1H, ser-
ꢂH), 4.40 (d, 1H, J ¼ 5:4 Hz, 3-OH), 4.92 (m, 2H, 3-H and ser-
(2S,3R,4S)-2,4-Dimethyl-1,3-octadacanediol (42). To a solu-
tion of the acetonide 41 (110 mg, 0.309 mmol) in MeOH (11.0
mL) at 0 ꢃC was added CSA (72 mg, 0.309 mmol), and the mixture
was stirred at room temperature for 23 h. The reaction mixture was
quenched by the addition of a saturated aqueous NaHCO3 solution
at 0 ꢃC, and the products were extracted with EtOAc. The organic

K. Kurosawa et al.
Bull. Chem. Soc. Jpn. Vol. 79, No. 6 (2006)
935
layer was washed with a saturated aqueous NaHCO3 solution and
brine, and then dried. Removal of the solvent left a residue, which
was purified by column chromatography (silica gel, 3 g, EtOAc/
hexane = 1/12 as eluent) to afford the 5-deoxy diol 42 (77 mg,
phy (silica gel, 7 g, EtOAc/hexane = 1/40 as eluent) to afford a
mixture (ca. 1.5:1) of 44 and its (3R)-isomer (53.4 mg, 89%) as a
colorless syrup; IR (neat) 3440, 3340, 1730, 1715 cmꢄ1; 1H NMR
(CDCl3, 300 MHz for the major isomer 44) ꢁ 0.01 (s, 6H), 0.78–
0.97 (m, 18H), 1.10–1.35 (m, 24H), 1.75 (m, 1H), 1.93 (m, 1H),
3.33 (m, 1H), 3.57 (m, 1H), 3.71 (m, 1H), 3.92 (m, 1H), 4.42–4.60
(m, 3H), 4.91 (m, 1H), 5.12 (s, 2H), 5.66 (d, 1H, J ¼ 8:8 Hz),
7.22–7.43 (m, 10H); FAB-HRMS Calcd for C40H74NO6Si ðM þ
HÞþ: 740.5285, Found m=z 740.5285.
21
79%) as a white solid; mp 43.0–44.8 ꢃC, ½ꢀꢁD þ10 (c 1.74,
CHCl3); IR (neat) 3320 cmꢄ1; 1H NMR (CDCl3, 300 MHz) ꢁ 0.79
(d, 3H, J ¼ 7:1 Hz, 2-Me), 0.86 (d, 3H, J ¼ 7:1 Hz, 4-Me), 0.87
(t, 3H, J ¼ 7:0 Hz, –(CH2)12CH3), 1.15–1.42 (m, 24H, –(CH2)12-
CH3), 1.60 (m, 3H, H-4, H-5, and H-50), 1.85 (dddq, 1H, J ¼ 9:0,
7.8, 3.4, and 7.1 Hz, H-2), 2.12–3.18 (m, 2H, 2 ꢅ OH), 3.46 (dd,
1H, J ¼ 9:0 and 2.4 Hz, H-3), 3.63 (dd, 1H, J ¼ 10:7 and 7.8 Hz,
H-1), 3.71 (dd, 1H, J ¼ 10:7 and 3.4 Hz, H-10); 13C NMR (CDCl3,
75 MHz) ꢁ 12.2, 13.5, 14.1, 22.7, 27.4, 29.4, 29.7, 29.9, 31.9,
34.0, 35.1, 37.3, 68.8, 80.3; FAB-HRMS Calcd for C20H43O2
ðM þ HÞþ: 315.3263, Found m=z 315.3283. Found: C, 76.14; H,
13.13%. Calcd for C20H42O2: C, 76.37; H, 13.46%.
An Inseparable Mixture of N-[(1,1-Dimethylethoxy)carbon-
yl]-L-valyl-L-threonyl-O-(phenylmethyl)-L-serine (1R,2S)-1-
[(1S)-2-[(1,1-Dimethylethyl)dimethylsilyl]oxy-1-methylethyl]-2-
methylhexadecyl Ester (45) and Its D-Serine Isomer. A mix-
ture (ca. 1.5:1) of 44 and its D-serine isomer (53 mg, 0.072 mmol)
in MeOH (5.3 mL) was stirred in the presence of 10% Pd on a car-
bon ethylenediamine complex (45 mg) under an atmospheric pres-
sure of H2 at room temperature for 1 h. The insoluble material was
removed by filtration and the filtrate was concentrated to give a
crude amine, which was dissolved in DMF (4.4 mL). To this solu-
tion at 0 ꢃC were added the dipeptide 25 (46 mg, 0.144 mmol),
Compound 42 from Natural Stevastelin C3. To a solution of
natural stevastelin C3 (3.2 mg, 0.0054 mmol) in THF (1 mL) at
0 ꢃC was added LiBH4 (1 mg, 0.046 mmol), and the mixture was
stirred at 80 ꢃC for 1 h. The reaction mixture was quenched by
the addition of H2O at 0 ꢃC, and then diluted with EtOAc. The
organic layer was washed with H2O, and then dried. Removal
of the solvent left a residue, which was purified by column chro-
matography (silica gel, 0.3 g, EtOAc/hexane = 1/12 as eluent) to
WSC HCl (33 mg, 0.173 mmol), and HOBt (23 mg, 0.173 mmol),
ꢂ
and the whole mixture was stirred at room temperature for 12 h.
The reaction mixture was diluted with EtOAc and washed succes-
sively with a saturated aqueous NH4Cl solution, a saturated aque-
ous NaHCO3 solution and brine, and then dried. Removal of the
solvent left a residue, which was purified by column chromatogra-
phy (silica gel, 1 g, acetone/toluene = 1/20 as eluent) to afford a
mixture (ca. 1.5:1) of the O-TBS ether 45 and its epimer (60 mg,
92%) as a colorless syrup; 1H NMR (CDCl3, 300 MHz for the ma-
jor isomer, 45) ꢁ 0.01 (s, 6H), 0.75–0.97 (m, 24H), 1.10–1.40 (m,
25H), 1.17 (d, 3H, J ¼ 6:3 Hz), 1.43 (s, 9H), 1.80–2.00 (m, 2H),
2.12 (m, 1H), 3.30 (dd, 1H, J ¼ 10:3 and 7.1 Hz), 3.48 (bs, 1H),
3.55 (dd, 1H, J ¼ 3:2 and 10.3 Hz), 3.68 (m, 1H), 3.90 (dd, 1H,
J ¼ 3:4 and 9.3 Hz), 3.97 (m, 1H), 4.34 (dq, 1H, J ¼ 2:7 and
6.3 Hz), 4.42–4.59 (m, 3H), 4.68 (m, 1H), 4.89 (dd, 1H, J ¼ 8:8
and 3.2 Hz), 5.07 (m, 1H), 6.87 (d, 1H, J ¼ 7:6 Hz), 7.15–7.40 (m,
6H); FAB-HRMS Calcd for C50H92N3O9Si ðM þ HÞþ: 906.6602,
Found m=z 906.6597.
1
afford 42 (0.4 mg, 24%) as a white solid. H NMR spectra were
fully identical with those of 42 prepared from 23.
(2S,3R,4S)-1-[[(1,1-Dimethylethyl)dimethylsilyl]oxy]-2,4-di-
methyl-3-octadacanol (43). To a solution of the diol 42 (87 mg,
0.276 mmol) in CH2Cl2 (4.3 mL) at 0 ꢃC were added Et3N
(0.155 mL, 1.10 mmol) and TBSCl (166 mg, 1.10 mmol), and the
mixture was stirred at room temperature for 1 h. The reaction mix-
ture was diluted with EtOAc and washed successively with a satu-
rated aqueous NH4Cl solution, a saturated aqueous NaHCO3 solu-
tion and brine, and then dried. Removal of the solvent left a res-
idue, which was purified by column chromatography (silica gel,
3 g, EtOAc/hexane = 1/50 as eluent) to afford the O-TBS ether
24
43 (115 mg, 97%) as a colorless syrup; ½ꢀꢁD þ16 (c 1.7, CHCl3);
1
IR (neat) 3510 cmꢄ1; H NMR (CDCl3, 300 MHz) ꢁ 0.08 (s, 6H),
0.77 (d, 3H, J ¼ 7:2 Hz), 0.87 (d, 3H, J ¼ 6:6 Hz), 0.88 (t, 3H,
J ¼ 6:6 Hz), 0.90 (s, 9H), 1.10–1.46 (m, 26H), 1.52 (m, 1H), 1.80
(dddq, 1H, J ¼ 8:7, 8.4, 3.9, and 7.2 Hz), 3.42 (ddd, 1H, J ¼ 8:7,
2.7, and 2.7 Hz), 3.59 (dd, 1H, J ¼ 9:9 and 8.4 Hz), 3.76 (dd, 1H,
J ¼ 9:9 and 3.7 Hz), 3.76 (d, 1H, J ¼ 2:7 Hz); 13C NMR (CDCl3,
75 MHz) ꢁ ꢄ5:6, ꢄ5:6, 12.4, 13.3, 14.1, 18.1, 22.7, 25.8, 27.6,
29.4, 29.7, 30.0, 31.9, 34.1, 35.3, 37.3, 69.5, 79.6; FAB-HRMS
Calcd for C26H57O2Si ðM þ HÞþ: 429.4128, Found m=z 429.4132.
Found: C, 72.94; H, 12.97%. Calcd for C26H56O2Si: C, 72.82; H,
13.16%.
An Inseparable Mixture of (3S,6R,7S)-7,10,10,11,11-Penta-
methyl-6-[(1S)-1-methylpentadecyl]-4-oxo-3-[(phenylmethoxy)-
methyl]-5,9-dioxa-2-aza-10-siladodecanoic Acid Phenylmethyl
Ester (44) and Its (3R)-Isomer. To a solution of the O-TBS
ether 43 (34.6 mg, 0.0807 mmol), Cbz–Ser(Bzl) (53.1 mg, 0161
mmol), and DMAP (19.7 mg, 0.161 mmol) in THF (3.46 mL) un-
der Ar at 0 ꢃC were added 2,4,6-trichlorobenzoyl chloride (0.038
mL, 0.242 mmol) and Et3N (0.057 mL, 0.403 mmol), and the mix-
ture was stirred at 0 ꢃC for 1.5 h. To the reaction mixture was add-
ed a saturated aqueous NH4Cl solution at 0 ꢃC, and the products
were extracted with EtOAc. The organic layer was washed succes-
sively with a saturated aqueous NH4Cl solution, a saturated aque-
ous NaHCO3 solution and brine, and then dried. Removal of the
solvent left a residue, which was purified by column chromatogra-
N-[(1,1-Dimethylethoxy)carbonyl]-L-valyl-L-threonyl-O-(phen-
ylmethyl)-L-serine (1R,2S)-1-[(1S)-2-Hydroxy-1-methylethyl]-
2-methylhexadecyl Ester (46) and Its D-Serine Isomer (47).
A solution of a mixture (ca. 1.5:1) of 45 and its D-serine isomer
(60 mg, 0.067 mmol) in acetic acid (8.4 mL), H2O (3.6 mL), and
THF (1.8 mL) was stirred at room temperature for 12 h. The reac-
tion mixture was diluted with H2O, and to this solution was added
solid NaHCO3 (15 g) at 0 ꢃC. The products were extracted with
EtOAc, and the organic layer was washed with a saturated aque-
ous NaHCO3 solution and brine, and then dried. Removal of the
solvent left a residue, which was purified by column chromatogra-
phy (silica gel, 4 g, acetone/toluene = 1/7 as eluent) to first af-
24
ford 47 (16 mg, 30%) as a colorless syrup. ½ꢀꢁD ꢄ29 (c 0.6,
CHCl3); IR (neat) 3300, 1740, 1720, 1640 cmꢄ1
;
1H NMR
(CDCl3, 300 MHz) ꢁ 0.86 (d, 3H, J ¼ 6:8 Hz), 0.88 (t, 3H, J ¼
6:1 Hz), 0.91 (d, 3H, J ¼ 6:6 Hz), 0.95 (d, 3H, J ¼ 6:8 Hz), 0.96
(d, 3H, J ¼ 7:3 Hz), 1.16 (d, 3H, J ¼ 6:3 Hz), 1.11–1.33 (m, 26H),
1.44 (s, 9H), 1.73 (m, 1H), 1.82 (m, 1H), 2.18 (m, 1H), 2.43 (m,
1H), 3.34–3.63 (m, 3H), 3.68 (dd, 1H, J ¼ 3:4 and 9.5 Hz), 3.94
(dd, 1H, J ¼ 2:9 and 9.5 Hz), 3.98 (m, 1H), 4.32–4.49 (m, 2H),
4.49 (d, 1H, J ¼ 12:2 Hz), 4.54 (d, 1H, J ¼ 12:2 Hz), 4.72 (ddd,
1H, J ¼ 2:9, 3.4, and 8.1 Hz), 4.86 (dd, 1H, J ¼ 2:9 and 9.0 Hz),
5.04 (d, 1H, J ¼ 7:3 Hz), 6.98 (d, 1H, J ¼ 7:3 Hz), 7.22–7.39 (m,
5H), 7.41 (d, 1H, J ¼ 8:1 Hz); 13C NMR (CDCl3, 75 MHz) ꢁ 13.2,

936 Bull. Chem. Soc. Jpn. Vol. 79, No. 6 (2006)
Total Synthesis of Stevastelins
14.1, 14.2, 17.6, 18.6, 19.3, 22.7, 27.1, 28.2, 29.4, 29.7, 30.4, 31.9,
33.8, 33.9, 36.9, 53.3, 57.7, 60.3, 64.1, 66.7, 69.2, 73.5, 80.3, 80.4,
127.9, 127.9, 128.4, 137.0, 156.0, 170.7, 171.1, 172.6; FAB-
HRMS Calcd for C44H78N3O9 ðM þ HÞþ: 792.5738, Found
m=z 792.5755. Found: C, 66.36; H, 9.68; N, 5.12%. Calcd for
C44H77N3O9: C, 66.72; H, 9.80; N, 5.30%.
(m, 2H, H-4 and val-ꢂH), 2.31 (m, 1H, H-50), 2.79 (m, 1H, H-2),
3.74–3.88 (m, 2H, thr-ꢀH and ser-ꢂH), 4.00–4.20 (m, 2H, val-ꢀH
and ser-ꢂ0H), 4.46 (d, 1H, J ¼ 10:7 Hz, OCHHPh), 4.50 (m, 1H,
thr-ꢂH), 4.55 (d, 1H, J ¼ 10:7 Hz, OCHHPh), 4.58–4.68 (m, 2H,
ser-ꢀH and H-3), 5.64 (d, 1H, J ¼ 9:0 Hz, val-NH), 7.08 (d, 1H,
J ¼ 7:3 Hz, thr-NH), 7.17–7.42 (m, 6H, Ph and ser-NH);
13C NMR (CDCl3, 75 MHz) ꢁ 14.1, 15.6, 18.4, 19.7, 20.6, 22.7,
26.4, 27.3, 29.4, 29.6, 29.7, 29.9, 31.9, 32.9, 34.8, 41.0, 53.4,
65.9, 70.0, 74.1, 82.8, 128.2, 128.6, 128.7, 137.3, 169.5, 172.9,
173.5; FAB-HRMS Calcd for C39H66N3O7 ðM þ HÞþ: 688.4901,
Found m=z 688.4904.
Further elution gave 46 (24 mg, 46%) as a colorless syrup;
21
½ꢀꢁD ꢄ27 (c 1.0, CHCl3); IR (neat) 3300, 1740, 1690, 1640
cmꢄ1
;
1H NMR (CDCl3, 300 MHz) ꢁ 0.86 (d, 3H, J ¼ 6:8 Hz),
0.88 (t, 3H, J ¼ 6:3 Hz), 0.89 (d, 3H, J ¼ 6:3 Hz), 0.93 (d, 3H,
J ¼ 7:1 Hz), 0.96 (d, 3H, J ¼ 7:3 Hz), 1.10–1.32 (m, 26H), 1.18
(d, 3H, J ¼ 6:3 Hz), 1.43 (s, 9H), 1.72 (m, 1H), 1.89 (m, 1H), 2.12
(dqq, 1H, J ¼ 7:1, 5.4, and 6.3 Hz), 2.49 (m, 1H), 3.35–3.60 (m,
3H), 3.69 (dd, 1H, J ¼ 3:2 and 9.5 Hz), 3.91 (dd, 1H, J ¼ 3:4
and 9.5 Hz), 3.99 (dd, 1H, J ¼ 5:4 and 8.1 Hz), 4.35 (dq, 1H, J ¼
2:4 and 6.3 Hz), 4.47 (dd, 1H, J ¼ 2:4 and 7.3 Hz), 4.52 (s, 2H),
4.71 (ddd, 1H, J ¼ 3:2, 3.4, and 8.3 Hz), 4.90 (dd, 1H, J ¼ 2:4
and 9.5 Hz), 5.11 (d, 1H, J ¼ 8:1 Hz), 7.00 (d, 1H, J ¼ 7:3 Hz),
7.26–7.40 (m, 5H), 7.38 (d, 1H, J ¼ 8:3 Hz); 13C NMR (CDCl3,
75 MHz) ꢁ 13.0, 14.0, 14.1, 17.7, 18.2, 19.2, 22.7, 27.2, 28.3, 29.3,
29.7, 30.6, 31.9, 33.7, 33.9, 36.9, 53.0, 57.0, 60.1, 64.3, 66.7, 69.3,
73.5, 79.7, 80.2, 127.8, 127.9, 128.4, 137.0, 155.9, 170.7, 170.7,
172.4; FAB-HRMS Calcd for C44H78N3O9 ðM þ HÞþ: 792.5738,
Found m=z 792.5748. Found: C, 66.39; H, 9.77; N, 5.12%. Calcd
for C44H77N3O9: C, 66.72; H, 9.80; N, 5.30%.
Stevastelin C3, Revised Structure (4). A mixture of the mac-
rocycle 49 (1.4 mg, 0.002 mmol) and 10% Pd on carbon (4.6 mg)
in MeOH (0.3 mL) was stirred at room temperature under an
atmospheric pressure of H2 for 3 h. The insoluble material was re-
moved by filtration, and the filtrate was concentrated to give a res-
idue, which was purified by column chromatography (silica gel,
0.3 g, MeOH/CHCl3 = 1/30 as eluent) to afford 4 (1.0 mg, 83%)
25
as an amorphous solid; ½ꢀꢁD ꢄ67 (c 0.13, MeOH), {natural ste-
27
vastelin C3, ½ꢀꢁD ꢄ66 (c 0.305, MeOH) (measured in our labo-
1
ratory)}; H NMR (DMSO-d6, 300 MHz) ꢁ 0.59 (d, 3H, J ¼ 6:8
Hz, 4-Me), 0.85 (t, 3H, J ¼ 6:8 Hz, –(CH2)12CH3), 0.87 (d, 3H,
J ¼ 6:3 Hz, val-Me), 0.92 (d, 3H, J ¼ 6:6 Hz, val-Me), 1.07 (d,
3H, J ¼ 6:3 Hz, thr-Me), 1.10 (d, 3H, J ¼ 7:6 Hz, 2-Me), 1.13–
1.30 (m, 25H, H-5 and –(CH2)12CH3), 1.49 (m, 1H, H-50), 1.74
(m, 1H, H-4), 2.05 (m, 1H, val-ꢂH), 2.74 (m, 1H, H-2), 3.54
(m, 1H, ser-ꢂH), 3.92 (m, 1H, ser-ꢂH), 4.03 (m, 2H, val-ꢀH
and thr-ꢂH), 4.13 (dd, 1H, J ¼ 10:3 and 2.4 Hz, thr-ꢀH), 4.61
(m, 2H, ser-ꢀH and H-3), 5.04 (dd, 1H, J ¼ 5:1 and 4.9 Hz, ser-
OH), 5.16 (d, 1H, J ¼ 4:6 Hz, thr-OH), 7.52 (m, 1H, val-NH),
7.85 (m, 2H, ser-NH and thr-NH); 13C NMR (DMSO-d6, 75 MHz)
ꢁ 13.9 (2-CH3 and 18-C), 15.4 (4-CH3), 18.9 and 19.3 (val-CH3),
21.0 (thr-CH3), 22.1, 25.9, 28.7, 28.9, 29.0, 29.2, 31.3, 32.3 (5–
17-C, val-ꢂC), 34.4 (4-C), 42.1 (2-C), 53.7 (ser-ꢀC), 59.5 (thr-
ꢀC), 61.00 (ser-ꢂC), 61.02 (val-ꢀC), 65.2 (thr-ꢂC), 80.5 (3-C),
170.0, 170.4 and 170.8 (ser-CO, thr-CO, val-CO, 1-C); FAB-
HRMS Calcd for C32H60N3O7 ðM þ HÞþ: 598.4431, Found m=z
598.4422. The 1H and 13C NMR data were fully identical with
those of natural stevastelin C3.
Cyclo[(2R,3R,4S)-3-hydroxy-2,4-dimethyloctadecanoyl-L-
valyl-L-threonyl-O-(phenylmethyl)-L-seryl] (49). To a solution
of the diol 46 (16 mg, 0.020 mmol) in CH2Cl2 (3.1 mL) at 0 ꢃC
were added TEMPO (1.24 g Lꢄ1 solution in CH2Cl2; 0.025 mL),
KBr (5.96 g Lꢄ1 solution in H2O; 0.039 mL), NaOCl (0.35 M solu-
tion in H2O; 0.068 mL), and NaHCO3 (50 g Lꢄ1 solution in H2O;
0.068 mL). After being stirred at 0 ꢃC for 1 h, to the reaction mix-
ture was added a 20% aqueous Na2S2O3 solution. The products
were extracted with CHCl3, and the organic layer was washed
with a 20% aqueous Na2S2O3 solution, and then dried. Removal
of the solvent gave a crude aldehyde (16 mg), which was dissolved
in t-BuOH (2.5 mL) and H2O (0.6 mL). To this solution were add-
ed NaH2PO4 2H2O (12 mg, 0.078 mmol), HOSO2NH2 (9.5 mg,
ꢂ
0.098 mmol), and NaClO2 (11 mg, 0.117 mmol), and the mixture
was stirred at 0 ꢃC for 30 min. To the reaction mixture at 0 ꢃC
was added a 1 M aqueous citric acid solution, and the products
were extracted with CHCl3. The organic layer was washed with
a 1 M aqueous citric acid solution, and then dried. Removal of
the solvent gave a crude carboxylic acid, which was dissolved
in CH2Cl2 (2.4 mL). To this solution under Ar at ꢄ18 ꢃC was add-
ed TFA (0.474 mL), and the mixture was stirred at ꢄ18 ꢃC for 1 h.
The reaction mixture was concentrated and dried in vacuo to give
We thank Dr. T. Nishikiori (Pharmaceutical Group, Nippon
Kayaku Co., Ltd., Tokyo, Japan) for providing us with natural
stevastelins B, B3, and C3. This work was supported by
Grants-in-Aid for Scientific Research on Priority Area ‘‘Crea-
tion of Biologically Functional Molecules,’’ and Grants-in-Aid
for the 21st Century COE program ‘‘KEIO LCC’’ from the
Ministry of Education, Culture, Sports, Science and Technolo-
gy, Japan.
crude 48 TFA, which was dissolved in DMF (9.8 mL). To this so-
ꢂ
lution under Ar at 0 ꢃC were added DEPC (0.0088 mL, 0.058
mmol) and Et3N (0.0096 mL, 0.069 mmol), and the mixture was
stirred at 0 ꢃC for 30 min, and then at room temperature for
13 h. The reaction mixture was diluted with EtOAc and washed
successively with a 1 M aqueous HCl solution, a saturated aque-
ous NaHCO3 solution and brine, and then dried. Removal of the
solvent left a residue, which was purified by column chromatogra-
phy (silica gel, 1 g, acetone/toluene = 1/10 as eluent) to afford
References
1
T. Morino, A. Masuda, M. Yamada, M. Nishimoto, T.
Nishikiori, S. Saito, N. Shimada, J. Antibiot. 1994, 47, 1341.
T. Morino, K. Shimada, A. Masuda, M. Nishimoto, S.
Saito, J. Antibiot. 1996, 49, 1049.
a) T. Morino, K. Shimada, A. Masuda, N. Yamashita, M.
2
3
26
49 (3.7 mg, 28% from 46) as a colorless syrup; ½ꢀꢁD ꢄ64 (c
Nishimoto, T. Nishikiori, S. Saito, J. Antibiot. 1996, 49, 564.
b) K. Shimada, T. Morino, A. Masuda, M. Sato, M. Kitagawa,
S. Saito, J. Antibiot. 1996, 49, 569.
0.1, CHCl3); IR (neat) 3390, 3270, 1740, 1665 cmꢄ1 1H NMR
;
(CDCl3, 300 MHz) ꢁ 0.77 (d, 3H, J ¼ 6:8 Hz, 4-Me), 0.79 (d, 3H,
J ¼ 6:9 Hz, 2-Me), 0.83 (d, 3H, J ¼ 7:1 Hz, val-Me), 0.88 (t, 3H,
J ¼ 6:1 Hz, –(CH2)12CH3), 0.99 (d, 3H, J ¼ 6:3 Hz, val-Me),
1.10–1.80 (m, 28H, thr-Me, H-5, and –(CH2)12CH3), 1.90–2.25
4
5
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