C-24 stereochemistry of marine sterols: (22E)-24-(isopropenyl)-22- dehydrocholesterol and 24-isopropenylcholesterol

Article abstract of DOI:10.1248/cpb.54.1473

The C-24 configuration of (22E,24ξ)-24-isopropenyl-22-dehydrocholesterol (1), which was recently isolated from the Colombian Caribbean sponge, Topsentia ophiraphidites, was investigated. Synthesis of the stereodefined (24R)- and (24S)-(22E)-24-isopropenyl-22-dehydrocholesterols (1a, 1b) followed by ¹H- and ¹³C-NMR data comparison of these sterols established the (24R)-configuration of 1. In addition, (24R)- and (24S)-24-isopropenylcholesterols (2a and 2b) were also synthesized and their NMR data are provided. The C-24 configurations of the samples of 24-isopropenylcholesterol reported previously are discussed.

Full text of DOI:10.1248/cpb.54.1473

October 2006
Notes
Chem. Pharm. Bull. 54(10) 1473—1477 (2006)
1473
C-24 Stereochemistry of Marine Sterols: (22E)-24-(Isopropenyl)-22-
dehydrocholesterol and 24-Isopropenylcholesterol
Shizue ECHIGO,a Noriyuki HARA,a Gladys Jeanette CARDERON,b Carmenza DUQUE,b and
,a
*
Yoshinori FUJIMOTO
a Department of Chemistry and Materials Science, Tokyo Institute of Technology; O-okayama, Meguro-ku, Tokyo
152–8551, Japan: and b Departamento de Química, Universidad Nacional de Colombia; AA 14490, Bogotá, Colombia.
Received June 22, 2006; accepted July 20, 2006; published online July 31, 2006
The C-24 configuration of (22E,24x)-24-isopropenyl-22-dehydrocholesterol (1), which was recently isolated
from the Colombian Caribbean sponge, Topsentia ophiraphidites, was investigated. Synthesis of the stereodefined
1
(24R)- and (24S)-(22E)-24-isopropenyl-22-dehydrocholesterols (1a, 1b) followed by H- and 13C-NMR data com-
parison of these sterols established the (24R)-configuration of 1. In addition, (24R)- and (24S)-24-isopropenylcho-
lesterols (2a and 2b) were also synthesized and their NMR data are provided. The C-24 configurations of the
samples of 24-isopropenylcholesterol reported previously are discussed.
Key words marine sterol; 24-isopropenyl-22-dehydrocholesterol; Topsentia ophiraphidites; 24-isopropenylcholesterol; nerve-
sterol
We have recently isolated a series of multiply alkylated uration at C-24 of 4a was assigned as R from the previous
sterols, including a new C31-sterol, ophirasterol [(22E)-24-(1- examples of orthoester Claisen rearrangements of steroidal
buten-2-yl)cholesta-5,22-dien-3b-ol], from the Caribbean (23E)-23-en-22-ols.3—5) The rearranged product 4a was re-
sponge, Topsentia ophiraphidites.1) Among these sterols, the duced with LiAlH4 to give the primary alcohol 5a, dehydra-
C-24 configurations of ophirasterol,1) (22E)-24-ethyl-24- tion of which gave the (24R)-exomethylene 6a. Acidic treat-
methyl-22-dehydrocholesterol and 24-ethyl-24-methyl- ment of 6a furnished the (24R)-sterol 1a. The (24S)-epimer
cholesterol were determined to be R, R and S, respectively, 1b was synthesized in the same manner from the (22S)-al-
through synthetic and X-ray studies.2) We have now investi- lylic alcohol 3b via the intermediates, the rearranged ester
gated the C-24 configuration of (22E,24x)-24-isopropenyl- 4b, the primary alcohol 5b, and the exomethylene 6b.
22-dehydrocholesterol 1 (Fig. 1). The isolation of 1 was re-
Hydrogenation of the primary alcohol 5a followed by de-
ported also from other marine sources and a terrestrial plant hydration gave the 22-saturated exomethylene 7a. Compound
(vide infra). NMR comparison of the natural 1 and synthetic, 7a furnished (24S)-24-isopropenylcholesterol 2a by regener-
stereodefined (24R)- and (24S)-samples led to the stereo- ation of the D5-3b-hydroxy system. Similarly, (24S)-alcohol
chemical assignment of 1. Stereochemically defined (24R)- 5b was converted to (24R)-epimer 2b via (24R)-exomethyl-
and (24S)-24-isopropenylcholesterols (2a, b) were also syn- ene 7b.
thesized and the C-24 configurations of the samples of (24x)-
With stereodefined (24R)- and (24S)-(22E)-D22-24-iso-
24-isopropenylcholesterol 2 reported previously are dis- propenylcholesterols (1a, b) in hand, their NMR data were
1
cussed.
compared with those of natural sample 1. The H and 13C
(24R)- and (24S)-(22E)-D22-24-isopropenylcholesterols signals were assigned by 2D-NMR studies including het-
(1a, b) and (24S)- and (24R)-24-isopropenylcholesterols eronuclear multiple-bond correlation (HMBC) spectra. The
1
(2a, b) were synthesized stereoselectively in a route involv- high-resolution H-NMR data (Table 1) were useful for dis-
ing orthoester Claisen rearrangement (Chart 1). The known tinguishing the epimers and considerable chemical shift dif-
starting materials, (22R)- and (22S)-allylic alcohols 3a and ference (Dd 0.021) was observed in the 21-H3 signals (d
3b,3) were used in our recent synthesis of ophirasterol and its 1.025 for 1a, d 1.004 for 1b). The olefinic protons, H-22 and
C-24 epimer.1) Exposure of 3a to a condition of orthoester H-23, also showed diagnostic difference as illustrated in Fig.
Claisen rearrangement (triethyl orthopropionate and a cat- 2. The H-22 and H-23 signals of (24S)-compound 1b showed
alytic amount of propionic acid in refluxing xylene) gave the a larger chemical shift difference than those of (24R)-epimer
(24R)-rearranged ester 4a as a ca. 1 : 1 mixture at the C-28 1a. The H-22 and H-23 signals of ophirasterol and its C-24
position, as revealed by 13C-NMR analysis of 4a. The config- epimer displayed an essentially identical pattern.1)
The 13C-NMR data (Table 2) of 1a and 1b are reported for
the first time. The C-16 signal showed the largest chemical
shift difference (0.47 ppm) with the C-16 of 1a being more
shielded, as shown in a graphic representation of 13C compar-
ison of the epimers (Fig. 3). The C-17 resonance showed the
second largest difference (0.22 ppm) with the C-17 of 1b
being more shielded. This aptitude is the same as that ob-
served for ophirasterol and its C-24 epimer.1) Analogously,
the C-16 signals of stigmasterol and crinosterol resonated at
Fig. 1. Structures of (22E,24x)-24-Isopropenyl-22-dehydrocholesterol (1)
and (24x)-24-Isopropenylcholesterol (2)
lower field than the corresponding C-24 epimers, polifera-
The C-24 configuration of 1 isolated from Topsentia ophiraphidites was established
to be R in the present study.
sterol and brassicasterol.6)
∗ To whom correspondence should be addressed. e-mail: fujimoto@cms.titech.ac.jp
© 2006 Pharmaceutical Society of Japan

1474
Vol. 54, No. 10
Chart 1. Synthesis of 24-Isopropenylsterols 1a, 1b, 2a and 2b
Table 1. 1H-NMR Data (500 MHz, in CDCl3) for Compounds 1, 1a and
1b
No.
1
1a (24R)
3.52 (m)
5.35 (br d, 5.2)
0.690 (s)
1b (24S)
3.52 (m)
5.35 (br d, 5.3)
0.697 (s)
3
6
3.52 (m)
5.35 (br d, 5.2)
18 0.689 (s)
19 1.008 (s)
1.008 (s)
1.010 (s)
21 1.025 (d, 6.6)
22 5.229 (m)
23 5.229 (m)
26 0.820 (d, 7.2)
27 0.835 (d, 6.9)
1.025 (d, 6.6)
5.229 (m)
5.229 (m)
0.821 (d, 7.1)
0.835 (d, 6.9)
1.004 (d, 5.8)
5.203 (dd, 15.1, 8.1)
5.263 (dd, 15.1, 8.4)
0.823 (d, 6.7)
0.837 (d, 6.7)
29 4.66 (br s), 4.68 (br s) 4.66 (br s), 4.68 (br s) 4.66 (br s), 4.69 (br s)
30 1.646 (s)
1.645 (s)
1.651 (s)
The H- and 13C-NMR data of the marine sterol 1 were in
excellent agreement with those of 1a (Tables 1, 2), thus es-
tablishing the C-24 configuration of the natural sterol 1 as R.
Melting point of 1 (149—151 °C, measured after the sample
(143—146 °C) described in our previous paper1) was recrys-
tallized from MeOH once more) further confirmed this as-
signment (mp: 150—152 °C for 1a; 174—176 °C for 1b).
Kikuchi et al. reported the isolation of (22E,24x)-24-iso-
propenyl-22-dehydrocholesterol (nervisterol) from the Orchi-
daceous plant, Nervilia purpurea.7) The C-24 configuration
1
1
Fig. 2. Partial H-NMR Spectra (500 MHz, CDCl3) of the Sample 1 from
Topsentia ophiraphidites (Top), 1a (Middle) and 1b (Bottom)
1
of nervisterol was now assigned as S on the basis of the H-
NMR data comparison and the reported mp (175—177 °C).
(22E)-24-Isopropenyl-22-dehydrocholesterol isolated from

October 2006
1475
Table 2. 13C-NMR Data (125 MHz, in CDCl3) for Compounds 1, 1a, 1b,
2a and 2b
Table 3. 1H-NMR Data (500 MHz, in CDCl3) for Compounds 2a and 2b16)
No.
2a (24S)
2b (24R)
No.
1
1a (24R)
1b (24S)
2a (24S)
2b (24R)
3
6
3.53 (m)
5.35 (br d, 5.1)
0.665 (s)
3.52 (m)
5.35 (br d, 5.6)
0.673 (s)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
37.25
31.67
71.81
42.31
140.74
121.69
31.89
31.89
50.15
36.51
21.06
39.65
42.28
56.78
24.30
28.43
56.12
12.03
19.39
40.11
21.19
137.75
128.58
58.44
29.18
20.14
20.75
148.25
110.10
20.34
37.26
31.66
71.78
42.31
140.75
121.67
31.89
31.89
50.16
36.51
21.06
39.66
42.28
56.79
24.30
28.43
56.13
12.04
19.39
40.11
21.19
137.75
128.59
58.44
29.18
20.14
20.76
148.22
110.10
20.34
37.26
31.67
71.80
42.31
140.76
121.68
31.90
31.90
50.16
36.51
21.07
39.67
42.26
56.84
24.37
28.90
55.91
12.02
19.38
40.30
21.29
137.80
128.71
58.57
29.33
20.24
20.78
148.35
110.08
20.47
37.24
31.65
71.79
42.29
140.74
121.71
31.89
31.89
50.11
36.49
21.06
39.72
42.27
56.72
24.27
28.13
55.87
11.82
19.39
36.20
19.06
34.17
26.27
55.49
30.23
20.85
21.50
147.36
111.86
18.91
37.24
31.65
71.80
42.32
140.74
121.72
31.88
31.90
50.10
36.49
21.08
39.78
42.29
56.76
24.27
28.16
56.18
11.84
19.39
35.47
18.59
33.94
26.20
55.02
30.23
20.85
21.61
147.08
112.03
18.51
18
19
21
26
27
29
30
1.006 (s)
1.007 (s)
0.922 (d, 6.6)
0.802 (d, 6.1)
0.910 (d, 5.9)
4.60 (br s), 4.74 (br s)
1.564 (s)
0.909 (d, 6.4)
0.799 (d, 6.4)
0.904 (d, 6.4)
4.61 (br s), 4.74 (br s)
1.561 (s)
Fig. 4. Comparison of the 13C-NMR Data of 2a and 2b
1
((24S)-24-ethylcholesterol). The reported H-NMR values of
the plant sterol are in good agreement with those of 2a, thus
confirming the previous stereochemical assignment. Catalan
et al. reported the isolation of a stereochemically pure (24S)-
24-isopropenylcholesterol 2a from the sponge, Aplysina fis-
tularis, the C-24 configuration of which was assigned on the
1
basis of the H-NMR data described above.10,11) (24S)-24-
Isopropenylcholesterol was also isolated from the sponge,
Pseudoaxinyssa sp.10) In contrast, 24-isopropenylcholesterol
isolated from a marine Chrysophyte12) could be assigned as
(24R)-compound 2b, because the reported 1H-NMR data
were in excellent agreement with those of 2b. Isolation of
(24x)-24-isopropenylcholesterol
2
from higher plants,
Anoectochilus koshunensis (Orchidaceae)13) and Azadirachta
indica (Meliacea),14) was recorded without relevant data to
assign the C-24 configuration.
Fig. 3. Comparison of the 13C-NMR Data of 1a and 1b
In conclusion, we have synthesized and provided detailed
the sponge Pseudoaxinyssa sp. was reportedly a C-24 1H- and 13C-NMR data for 24R- and 24S-epimers of 1 and 2,
epimeric mixture.8)
which allowed us to establish the C-24 configuration of 1 iso-
1
The H- and 13C-NMR data of the 22-saturated 24-iso- lated from T. ophiraphidites. The same 24b orientation (with
propenylcholesterols 2a and 2b are listed in Tables 3 and 2, regard to the 1-buten-2-yl and isopropenyl substituents) of
respectively. In the H-NMR spectra the 21-H3 (Dd 0.013) ophirasterol and (22E,24R)-24-isopropenyl-22-dehydrocho-
1
and 18-H3 (Dd 0.008) signals showed small differences and lesterol found in T. ophiraphidites would support the view
these differences can be used for determination of the C-24 that 1a is a biosynthetic precursor of ophirasterol in the
configuration when accurate 1H-NMR data are available. The sponge.1) The present study also determined the 24S configu-
13C-NMR data, reported for the first time in this paper, ration of nervisterol. It is notable that (24S)-24-isopropenyl-
1
seemed to be more diagnostic than the H-NMR data. The cholesterol 2a cannot be a precursor of nervisterol 1b in spite
signals of C-20 (Dd 0.73), C-21, C-24 and C-30 exhibited of their co-occurrence in the N. purpurea plant, since their C-
more than 0.3 ppm chemical shift differences between 24 orientations are different from each other. Stoilov et al. re-
epimers, as shown in Fig. 4.
ported experimental evidence that fucosterol/isofucosterol is
Kikuchi et al. reported the isolation of (24S)-24-iso- a biosynthetic precursor of the 24-isopropenylcholesterol in
propenylcholesterol from N. purpurea,7,9) the 24S configura- the sponge, Pseudoaxinissa sp.15) Neither 2a nor 2b was de-
tion of which was assigned by converting it to clionasterol tected in GLC and HPLC analysis of the sterol mixture ob-

1476
Vol. 54, No. 10
tained from T. ophiraphidites.
(22E,24S)-24-Isopropenylcholesta-5,22-dien-3b-ol
(1b) Compound
6b (52 mg, 118 mmol) was converted to 1b (43 mg, 87%) according to the
Experimental
procedure described above for the conversion of 6a to 1a. 1b: white needles,
General Melting points were determined by a Yazawa BY-1 hot-stage mp 174—176 °C. [a]D25 ꢁ46.3° (cꢀ2.07, CHCl3). H-NMR data: see Table
1
apparatus and are uncorrected. Optical rotations were measured with a
1. 13C-NMR data: see Table 2. Anal. Calcd for C30H48O: C, 84.84; H, 11.39.
1
JASCO DIP-360 polarimeter. H- and 13C-NMR spectra were recorded on a Found: C, 84.92; H, 11.69.
Bruker DRX500 (500 MHz for 1H and 125 MHz for 13C) or JEOL JNM-
(24S)-24-Isopropenyl-6b-methoxy-3a,5a-cyclocholestane (7a) A so-
LA400 (400 MHz for 1H and 100 MHz for 13C) spectrometer in CDCl3 solu- lution of 5a (37.5 mg, 82.1 mmol) in AcOEt (1.0 ml) was hydrogenated in the
tion. CDCl3 signal was used as a reference (d 77.0) for 13C-chemical shifts. presence of 10% Pd/C (15 mg) overnight. The catalyst was filtered off
EI-MS (70 eV) and HR-EI-MS spectra were obtained on a JEOL JMS-700 through a pad of Celite and the filtrate was concentrated in vacuo. The
1
spectrometer. A part of H-NMR data, d: 0.44 (dd, Jꢀ8.0, 5.1 Hz, 4a-H),
0.65 (t, Jꢀ4.4 Hz, 4b-H), 2.78 (br t, Jꢀ2.7 Hz, 6-H), 3.32 (s, OMe), for
compounds with a 6b-methoxy-3a,5-cyclo structure are not described, since
they were common to all such compounds.
residue was chromatographed on silica gel with hexane–ether (20 : 1) to give
the hydrogenated product (37 mg, 81.3 mmol) as an oil.
2-Nitrophenyl selenocyanate (55 mg, 244 mmol) and n-tributylphosphine
(61 ml, 244 mmol) were added to a solution of the hydrogenated product
(37 mg, 81.3 mmol) in THF (2.0 ml) and the mixture was stirred for 1 h
(22E,24R)-24-Isopropenyl-6b-methoxy-3a,5-cyclo-5a-cholest-22-ene
(6a) A solution of 22R-alcohol 3a1,3) (70 mg, 169 mmol) (1H-NMR d: 4.12 under N2. 30% H2O2 (1.0 ml) was added and the mixture was stirred for an-
(dd, Jꢀ7.4, 3.4 Hz, 22-H)), triethyl orthopropionate (100 ml, 507 mmol) and other 1 h. The mixture was diluted with ether and brine. The organic phase
propionic acid (7.5 ml, 101 mmol) in xylene (2.1 ml) was heated at reflux was washed with saturated aqueous NaHCO3 and brine, dried over Na2SO4,
under N2 for 1 h. After removal of most of the solvent on a rotary evaporator, and concentrated in vacuo. The residue was chromatographed on silica gel
the residue was chromatographed on silica gel with hexane–ether (20 : 1) to
1
with hexane–ether (20 : 1) to give 7a (22 mg, 60%, 2 steps) as oil. H-NMR
1
give the rearranged product 4a (71 mg) as oil. H-NMR d: 0.707/0.718 (s, d: 0.70 (s, 18-H3), 0.80 (d, Jꢀ6.1 Hz, 26-H3), 0.91 (d, Jꢀ6.1 Hz, 27-H3),
18-H3), 1.224/1.243 (t, Jꢀ7.1 Hz, OCH2CH3), 4.02—4.16 (m, OCH2CH3), 0.92 (d, Jꢀ6.6 Hz, 21-H3), 1.02 (s, 19-H3), 1.56 (s, 30-H3), 4.60 (br s, 29-
4.94—5.29 (m, 22-H, 23-H). 13C-NMR d: 59.91/59.98 (C-29),
124.53/125.20 (C-23), 140.31/141.17 (C-22), 176.21/176.74 (CꢀO).
LiAlH4 (16 mg, 142 mmol) was added to a solution of 4a (71 mg) at 0 °C
under N2 and the mixture was stirred for 30 min. The solution was diluted
Hb), 4.74 (br s, 29-Hb). 13C-NMR d: 12.20, 13.05, 18.88, 18.90, 19.29,
20.85, 21.48, 21.52, 22.77, 24.17, 24.96, 26.30, 28.24, 30.23, 30.46, 33.34,
34.15, 35.04, 35.28, 36.24, 40.24, 42.73, 43.37, 48.02, 55.50, 56.06, 56.50,
56.55, 82.43, 111.86, 147.37. HR-EI-MS m/z 440.4062 [Mꢂ]; C31H52O re-
with moist ether and then a small amount of water. The supernatant solution quires 440.4018.
was filtered through a pad of Celite and concentrated in vacuo. The residue
(24S)-24-Isopropenylcholest-5-en-3b-ol (2a) A solution of 7a (22 mg,
was chromatographed on silica gel with hexane–AcOEt (10 : 1) to give 5a 49.2 mmol) in dioxane (0.60 ml) and H2O (0.20 ml) containing p-TsOH·H2O
1
(48 mg, 105 mmol) as oil. H-NMR d: 0.73 (s, 18-H3), 3.33—3.65 (m, 29- (374 mg, 1.97 mmol) was heated at 105 °C for 2 h. Extractive (ether) work-up
H2), 5.05—5.27 (m, 22-H, 23-H). 13C-NMR d: 67.17/67.57 (C-29),
126.56/126.70 (C-23), 139.70/140.16 (C-22).
gave a crude product which was chromatographed on silica gel with
hexane–AcOEt (7 : 1) to give 2a as a solid. Recrystallization from MeOH af-
forded 2a (12 mg, 67%) as white plates, mp 134—135 °C. [a]D25 ꢁ37.6°
2-Nitrophenyl selenocyanate (71.5 mg, 315 mmol) and tri-n-butylphos-
phine (79 ml, 315 mmol) were added to a solution of 5a (48 mg, 105 mmol)
in THF (2.5 ml) and the mixture was stirred for 1 h under N2. 30% H2O2 Anal. Calcd for C30H50O: C, 84.44; H, 11.81. Found: C, 84.36; H, 12.01.
1
(cꢀ1.29, CHCl3). H-NMR data: see Table 3. 13C-NMR data: see Table 2.
(1.0 ml) was added and the mixture was stirred for another 1.5 h. The mix-
ture was diluted with ether and brine, and the organic layer was washed with Compound 5b (26 mg, 56.7 mmol) was converted to 7b (14 mg, 58%, 2
saturated aqueous NaHCO3 and brine, dried over Na2SO4, and concentrated
(24R)-24-Isopropenyl-6b-methoxy-3a,5-cyclo-5a-cholestane
(7b)
steps) according to the procedure described for 5a. 7b: oil. 1H-NMR d: 0.71
in vacuo. The residue was chromatographed on silica gel with hexane–ether (s, 18-H3), 0.80 (d, Jꢀ6.3 Hz, 26-H3), 0.90 (d, Jꢀ6.6 Hz, 27-H3), 0.91 (d,
1
(20 : 1) to give 6a (38 mg, 51%, 3 steps) as oil. H-NMR d: 0.73 (s, 18-H3), Jꢀ6.5 Hz, 21-H3), 1.02 (s, 19-H3), 1.56 (s, 30-H3), 4.61 (br s, 29-Ha), 4.74
0.82 (d, Jꢀ6.6 Hz, 26-H3), 0.83 (d, Jꢀ6.6 Hz, 27-H3), 1.02 (d, Jꢀ6.4 Hz, 21-
(br s, 29-Hb). 13C-NMR d: 12.23, 13.04, 18.51, 18.56, 19.30, 20.85, 21.51,
H3), 1.02 (s, 19-H3), 1.65 (s, 30-H3), 2.19 (m, 25-H), 4.66 (br s, 29-Ha), 4.68
21.62, 22.77, 24.17, 24.96, 26.26, 28.27, 30.23, 30.46, 33.33, 33.92, 35.00,
(br s, 29-Hb), 5.24 (m, 22-H, 23-H). 13C-NMR d: 12.42, 13.06, 19.29, 20.13, 35.29, 35.54, 40.28, 42.77, 43.37, 47.99, 55.04, 56.35, 56.50, 56.55, 82.42,
20.34, 20.74, 21.19, 21.44, 22.74, 24.19, 24.95, 28.55, 29.15, 30.46, 33.33, 112.30, 147.10. HR-EI-MS m/z 440.4038 [Mꢂ]; C31H52O requires 440.4018.
35.05, 35.23, 40.14, 40.19, 42.71, 43.37, 48.04, 56.26, 56.54, 58.43, 82.39,
110.09, 128.48, 137.82, 148.24. Anal. Calcd for C31H50O: C, 84.87; H, 31.8 mmol) was converted to 2b (10 mg, 74%) in the same manner as de-
(24R)-24-Isopropenylcholest-5-en-3b-ol (2b) Compound 7b (14 mg,
11.49. Found: C, 84.58; H, 11.51.
(22E,24R)-24-Isopropenylcholesta-5,22-dien-3b-ol (1a) A solution of
6a (37 mg, 84 mmol) in dioxane (1.2 ml) and H2O (0.40 ml) containing p- see Table 2. Anal. Calcd for C30H50O: C, 84.44; H, 11.81. Found: C, 84.18;
TsOH·H2O (64 mg, 3.4 mmol) was heated at 105 °C for 3 h. Extractive H, 11.86.
(ether) work-up gave a crude product which was chromatographed on silica
scribed for the conversion of 6a to 1a. 2b: white needles; mp 139—140 °C.
[a]D25 ꢁ37.8° (cꢀ0.98, CHCl3). H-NMR data: see Table 3. 13C-NMR data:
1
gel with hexane–AcOEt (7 : 1) to give 1a as a solid. Recrystallization from
MeOH afforded 1a (24 mg, 67%) as white plates, mp 150—152 °C. [a]D25
ꢁ41.7° (cꢀ2.59, CHCl3). 1H-NMR data: see Table 1. 13C-NMR data: see
Table 2. Anal. Calcd for C30H48O: C, 84.84; H, 11.39. Found: C, 84.76; H,
11.41.
Acknowledgments This work was supported in part by a Grant from
Colciencias to C. D.
References and Notes
1) Calderon G. J., Castellanos L., Duque C., Echigo S., Hara N., Fuji-
moto Y., Steroids, 69, 93—100 (2004).
2) Echigo S., Calderon G. J., Castellanos L., Duque C., Hara N., Fuji-
moto Y., Steroids, 72 (2007), in press.
3) Wiersig J. R., Waespe-Sarcevic N., Djerassi C., J. Org. Chem., 44,
3374—3382 (1979).
(22E,24S)-24-Isopropenyl-6b-methoxy-3a,5-cyclo-5a-cholest-22-ene
(6b) (22S)-Alcohol 3b1,3) (131 mg, 316 mmol) (1H-NMR d: 4.21 (br t,
Jꢀ5.2 Hz, 22-H)) was converted to 6b (59 mg, 42%, 3 steps) according to
the procedure described for 3a. The intermediate 4b: oil, 1H-NMR d:
0.710/0.717 (s, 18-H3), 1.232/1.244 (t, Jꢀ7.1 Hz, OCH2CH3), 3.99—4.15
(m, OCH2CH3), 4.96—5.25 (m, 22-H, 23-H). 13C-NMR d: 59.80/59.97 (C-
29), 124.80/125.17 (C-22), 140.35/141.03 (C-23), 176.18/176.61 (CꢀO).
5b: oil, 1H-NMR d: 0.72 (s, 18-H3), 3.36—3.63 (m, 29-H2), 5.04—5.26 (m,
22-H, 23-H), 13C-NMR d: 67.16/67.47 (C-29), 126.78/126.90 (C-23),
139.65/140.00 (C-22). 6b: mp 116—117 °C (recrystallized from MeOH),
1H-NMR d: 0.73 (s, 18-H3), 0.82 (d, Jꢀ6.6 Hz, 26-H3), 0.84 (d, Jꢀ6.6 Hz,
27-H3), 1.00 (d, Jꢀ6.6 Hz, 21-H3), 1.02 (s, 19-H3), 1.65 (s, 30-H3), 2.18 (m,
25-H), 4.66 (br s, 29-Ha), 4.68 (br s, 29-Hb), 5.23 (m, 22-H, 23-H), 13C-
NMR d: 12.41, 13.07, 19.28, 20.20, 20.50, 20.78, 21.29, 21.43, 22.74,
24.28, 24.95, 29.02, 29.29, 30.46, 33.33, 35.06, 35.22, 40.15, 40.38, 42.68,
43.37, 48.03, 56.04, 56.55, 56.59, 58.59, 82.39, 110.06, 128.64, 137.86,
148.36. Anal. Calcd for C31H50O: C, 84.87; H, 11.49. Found: C, 84.58; H,
11.51.
4) Sucrow W., Schubert B., Richter W., Slopianka M., Chem. Ber., 104,
3689—3703 (1971).
5) Khripach V. A., Zhabinskii V. N., Konstantinova O. V., Khripach N. B.,
Antonchick A. P., Schneider B., Steroids, 67, 597—603 (2002).
6) Wright J. L. C., McInnes A. G., Shimizu S., Smith D. G., Walter J. A.,
Idler D., Khalil W., Can. J. Chem., 56, 1898—1903 (1978).
7) Kikuchi T., Kadota S., Suehara H., Namba T., Chem. Pharm. Bull., 33,
2235—2242 (1985).
8) Tam Ha T. B., Kokke W. C. M. C., Proudfoot J. R., Djerassi C.,
Steroids, 45, 263—276 (1985).
9) Kadota S., Sima T., Kikuchi T., Chem. Pharm. Bull., 35, 200—210
(1987).
10) Catalan C. A. N., Thompson J. E., Kokke W. C. M. C., Djerassi C.,

October 2006
1477
Tetrahedron, 41, 1073—1085 (1985).
11) The sterol was originally reported as a C-24 epimeric mixture, but
13) Ito A., Yasumoto K., Kasai R., Yamasaki K., Phytochemistry, 36,
1465—1467 (1994).
later revised as a stereochemically pure material. Kokke W. C. M. C., 14) Selvi S. T., Mohan P. S., Indian J. Chem., 36B, 1082—1083 (1997).
Pak C. S., Fenical W., Djerassi C., Helv. Chim. Acta, 62, 1310—1318
(1979).
15) Stoilov I., Thompson J. E., Djerassi C., Tetrahedron, 42, 4147—4160
(1986).
12) Kokke W. C. M. C., Shoolery J. N., Fenical W., Djerassi C., J. Org.
Chem., 49, 3742—3752 (1984).
16) The spectra (higher field region) are reported in ref. 10.