Stereospecific synthesis of 1,2-dioxolanes by alkoxy radical β- fragmentation of steroidal cyclic peroxyhemiacetals

Article abstract of DOI:10.1021/jo980319q

A new one-post synthesis of 3,5-substituted 1,2-dioxolanes from six- membered cyclic peroxyhemiacetal derivatives of hexadydrobenzo[c][1,2]dioxin- 8a-ol is described. A number of steroidal peroxyhemiacetals, (2S,2'S,3R)- (11), (2S,2'R,3R/S)-(13), (2R,2'R,3R/S)-2(2'-hydroperoxypropyl-3'- phenylsulfonyl)-5α-cholestan-3-one 2',3-peroxyhemiacetal (17), and (2S,5R)- 2-hydroperoxy-3-phenylsulfonyl-4-nor-3,4-secocholestan-5-one 2,5- peroxyhemiacetal (24), have been prepared in order to test the scope and diastereoselectivity of the present methodology. These substrates were irradiated with visible light in the presence of (diacetoxyiodo)benzene and iodine to generate the corresponding alkoxy radical, which undergoes regioselective β-fission yielding a carbon radical, that further reacts in a stereoselective manner with an iodine atom to give a 10-membered peroxylactone. This iodide intermediate is intramolecularly substituted by the peroxide anion generated by intermolecular nucleophilic attack of a hydroxide or methoxide anion to the acyl carbon with concomitant carbon- oxygen bond cleavage. This operationally simple reaction permitted us to synthesize methyl (2S,2'S)-(33), (2S,2'R)-(34), (2R,2'R)-1-[5'- [(phenylsulfonyl)methyl]-[1',2']dioxolan-3'-yl]-2-nor-2,3-secocholestan-3- oate (36), and methyl (1'R,1'''R,3'aS,3''R,4'S,5'S,5''S,7'aR)-3-[5'-[5''- (phenylsulfonyl)methyl]-3''-methyl[1''2,2'']dioxolan-3''-yl]-1'-(1''',5'''- dimethylhexyl)-7'a-methyloctahydroinden-4'-yl]propanoate (37) in good yields.

Full text of DOI:10.1021/jo980319q

J . Org. Chem. 1998, 63, 4697-4705
4697
Ster eosp ecific Syn th esis of 1,2-Dioxola n es by Alk oxy Ra d ica l
â-F r a gm en ta tion of Ster oid a l Cyclic P er oxyh em ia ceta ls
Alicia Boto, Rosendo Herna´ndez,* Silvia M. Vela´zquez, and Ernesto Sua´rez*
Instituto de Productos Naturales y Agrobiologı´a del CSIC, Carretera de La Esperanza 3,
38206-La Laguna, Tenerife, Spain
Thierry Prange´
LURE, Universite´ Paris-Sud, Paris, 91405 Orsay Cedex, France
Received February 19, 1998
A new one-pot synthesis of 3,5-substituted 1,2-dioxolanes from six-membered cyclic peroxyhemiacetal
derivatives of hexahydrobenzo[c][1,2]dioxin-8a-ol is described. A number of steroidal peroxyhemi-
acetals, (2S,2′S,3R)-(11), (2S,2′R,3R/S)-(13), (2R,2′R,3R/S)-2-(2′-hydroperoxypropyl-3′-phenylsul-
fonyl)-5R-cholestan-3-one 2′,3-peroxyhemiacetal (17), and (2S,5R)-2-hydroperoxy-3-phenylsulfonyl-
4-nor-3,4-secocholestan-5-one 2,5-peroxyhemiacetal (24), have been prepared in order to test the
scope and diastereoselectivity of the present methodology. These substrates were irradiated with
visible light in the presence of (diacetoxyiodo)benzene and iodine to generate the corresponding
alkoxy radical, which undergoes regioselective â-fission yielding a carbon radical, that further reacts
in a stereoselective manner with an iodine atom to give a 10-membered peroxylactone. This iodide
intermediate is intramolecularly substituted by the peroxide anion generated by intermolecular
nucleophilic attack of a hydroxide or methoxide anion to the acyl carbon with concomitant carbon-
oxygen bond cleavage. This operationally simple reaction permitted us to synthesize methyl (2S,2′S)-
(33), (2S,2′R)-(34), (2R,2′R)-1-[5′-[(phenylsulfonyl)methyl]-[1′,2′]dioxolan-3′-yl]-2-nor-2,3-secocholestan-
3-oate (36), and methyl (1′R,1′′′R,3′aS,3′′R,4′S,5′S,5′′S,7′aR)-3-[5′-[5′′-(phenylsulfonyl)methyl]-3′′-
methyl[1′′,2′′]dioxolan-3′′-yl]-1′-(1′′′,5′′′-dimethylhexyl)-7′a-methyloctahydroinden-4′-yl]propano-
ate (37) in good yields.
1,2-Dioxolanes are found in biologically important
compounds such as antifungal marine natural products,1
prostaglandins, and oxidized lipids.2 However, despite
the significance of these compounds, only a small number
of synthetic procedures have been reported to date.
These methods basically rely upon cyclization of func-
tionalized hydroperoxides,3 dioxygenation of cyclopropane
rings,4 and 1,3-dipolar addition of carbonyl oxides5 or
hydroperoxycarbenium ions6 to alkenes.
The synthesis of 1,3-diols in a stereocontrolled manner
is of considerable interest because these subunits are
present in naturally occurring substances, such as poly-
ene macrolides,7 with an important degree of structural
complexity and significant physiological activity. 1,2-
Dioxolanes are adequate precursors of 1,3-diols through
reductive cleavage of the peroxide bond,8 although â-keto
alcohols can also be obtained.9 These last compounds can
be reduced in a diastereoselective manner to give syn-10
or anti-diols.11
Earlier reports from this laboratory have described the
synthesis of medium-sized lactones III via â-fragmenta-
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(b) Ichinose, N.; Mizuno, K.; Tamai, T.; Otsuji, Y. J . Org. Chem. 1990,
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S0022-3263(98)00319-3 CCC: $15.00 © 1998 American Chemical Society
Published on Web 06/12/1998

4698 J . Org. Chem., Vol. 63, No. 14, 1998
Boto et al.
Sch em e 1
iodine under irradiation with visible light provided a new
and efficient synthesis of 1,2-dioxolanes.18
Resu lts a n d Discu ssion
Syn th esis of P er oxyh em ia ceta ls. Substrates 11,
13, 17, and 24 to be used in this study were prepared
from γ,δ-unsaturated ketones 2, 3, and 7 following the
procedure of Yoshida and Isoe17e (vide infra). 2-Allyl-5R-
cholestan-3-one isomers 2 and 3 were obtained from 2â-
allyl-5R-cholestan-3R-ol (1), which in turn was prepared
by treatment of 2R,3R-epoxy-5R-cholestane19 with allyl-
magnesium bromide, essentially following a previously
reported procedure.20 Compound 1 was oxidized by
pyridinium chlorochromate21 to give 2. Treatment of
compound 2 with 0.5% methanolic NaOH afforded the
thermodynamic γ,δ-enone 3 in 85% yield from the 2R,3R-
epoxide (Scheme 2).
5-Oxo-4-nor-3,4-secocholest-2-ene (7) was prepared
from 5,5-(ethylenedioxy)-4-nor-3,4-secocholestan-3-ol (4)22
by treatment with o-nitrophenyl selenocyanate,23 in the
presence of tri-n-butylphosphine,24 to give the nitrophen-
ylseleno derivative 5 as a yellow noncrystalline solid, in
85% yield. The phenylseleno group of 5 underwent
oxidative syn elimination by selenoxide rearrangement,
with hydrogen peroxide,25 yielding enone 6. Finally, acid
cleavage of the protective ethylenedioxy carbonyl group
with p-toluenesulfonic acid in acetone afforded compound
7, in 55% overall yield from 4 (Scheme 2).
tion of alkoxy radicals generated by irradiation of hemi-
acetals of the type of octahydrochromen-8a-ol (Ia) in the
presence of a hypervalent organoiodine reagent12 (Scheme
1). When the reaction is carried out under an oxygen
atmosphere, the intermediate carbon radical IIb can be
peroxidated and the resulting peroxy radical can be
trapped by a conveniently positioned carbon-carbon or
carbon-oxygen double bond to give 1,2-dioxolanes13 or
â-peroxylactones,14 respectively. In a continuation of our
studies, we envisioned a conceptually simple methodology
for the construction of medium-sized peroxylactones,
which, to the best of our knowledge, are hitherto un-
known. This task could be accomplished by â-fragmenta-
tion of peroxyhemiacetal derivatives of hexahydrobenzo-
[c][1,2]dioxin-8a-ol (Ic) (Scheme 1), the sequence being
analogous to that for the synthesis of medium-sized
lactones III. In most cases, however, medium-sized
peroxylactones could not be isolated and the radical
intermediate IIc evolved to 1,2-dioxolane IV, presumably
by intramolecular cyclization of the peroxide function
promoted by nucleophilic hydroxide or methoxide ion
attack (vide infra).
In this paper, we report on the preparation of steroidal
(phenylsulfonyl)hydroperoxides 11, 13, 17, and 24 as
starting materials in order to explore the scope and regio-
and stereoselectivity of this new approach to the synthe-
sis of 1,2-dioxolanes. The synthesis of hydroperoxides
is a well-documented process,15 with a number of simple
ways to prepare hydroperoxides from olefins being de-
scribed in the literature.16 The hydroperoxide function
initially formed can be intramolecularly trapped by a
carbonyl group in the appropriate position to give the
corresponding cyclic peroxide derivatives of hexahydro-
benzo[c][1,2]dioxin-8a-ol.17 In fact, these peroxyhemiac-
etals on treatment with (diacetoxyiodo)benzene (DIB) and
(15) (a) Fielder, S.; Rowan, D. D.; Sherburn, M. S. Synlett 1996,
349-350. (b) Nakamura, E.; Sato, K.-i.; Imanishi, Y. Synlett 1995,
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Am. Chem. Soc. 1954, 76, 2987-2990.
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R. W.; Agarwal, S. K. J . Org. Chem. 1985, 50, 4698-4702. (d) Saito,
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1996, 37, 4949-4952. (b) Qian, C.-Y.; Nishino, H.; Kurosawa, K. J .
Heterocycl. Chem. 1993, 30, 209-216. (c) Yamada, T.; Iwahara, Y.;
Nishino, H.; Kurosawa, K. J . Chem. Soc., Perkin Trans. 1 1993, 609-
616. (d) Tategami, S.; Yamada, T.; Nishino, H.; Korp, J . D.; Kurosawa,
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Nakatani, S.; Sakaguchi, K.; Isoe, S. J . Org. Chem. 1989, 54, 3383-
3389. (g) Ensley, H. E.; Carr, R. V. C.; Martin, R. S.; Pierce, T. E. J .
Am. Chem. Soc. 1980, 102, 2836-2838. (h) Yoshida, J .; Sakaguchi, K.;
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Stereospecific Synthesis of 1,2-Dioxolanes
J . Org. Chem., Vol. 63, No. 14, 1998 4699
Sch em e 2a
Sch em e 4a
a
Key: (a) PhSH, O2, AcOH, rt, 48 h; (b) m-CPBA, CH2Cl2, rt,
1 h, 92%.
a
Key: (a) PCC, CH2Cl2, rt, 20 h, 79%; (b) NaOH (0.5%), MeOH,
Sch em e 5a
rt, 1 h, 95%; (c) o-NO2PhSeCN, n-Bu3P, THF, 5 h, 85%; (d) H2O2
(30%), THF, rt, overnight, 82%; (e) p-TsOH‚H2O, acetone, rt, 20
h, 78%.
Sch em e 3a
a
Key: (a) PhSH, O2, AcOH, rt, 45 h; (b) m-CPBA, CH2Cl2, rt,
45 min, 88-96%.
a
Key: (a) PhSH, O2, AcOH, rt, 36 h; (b) m-CPBA, CH2Cl2, rt,
Rea ction of γ,δ-Un sa tu r a ted Keton es 2, 3, a n d 7
w ith Molecu la r Oxygen a n d Ben zen eth iol. The
following general procedure17e was used to prepare the
peroxyhemiacetals 11, 13, 17, and 24. Enone 3, in acetic
acid, was treated with benzenethiol (ca. 4 equiv), while
a stream of oxygen was bubbled through the solution at
room temperature to give (2′S)- and (2′R)-peroxyhemi-
acetals 10 and 12, in 28 and 25% yield, respectively, the
latter as an inseparable mixture (9:1) of cis- and trans-
fused AA′ rings. Moreover, the sulfide 8 from benzene-
thiol reduction of the C-2′ radical intermediate, and the
diketone 9, formed by the acid-catalyzed rearrangement
of the C-2′ hydroperoxide, were also obtained as minor
products (Scheme 3). Sulfides 10 and 12 were oxidized
with m-CPBA to the corresponding sulfones 11 and 13
in excellent yields.
The reaction of enone 2 with the benzenethiol/O2
system proceeded to give, apart from sulfide 14, the
expected peroxyhemiacetals 15 and 16, albeit in low yield
(Scheme 4). The reaction was more complex than that
previously reported because in the acidic reaction condi-
tions the enone 2 partially isomerized to enone 3, and
hence, peroxyhemiacetals 10 and 12 were also obtained
in 8 and 4% yield, respectively. Sulfone 17 was obtained
by oxidation of sulfide 16, but all attempts to oxidize
30 min, 95%.
sulfide 15 proved to be unsuccessful, giving rise to a
complex mixture of products that was not studied.
When the peroxidation reaction was conducted with
the enone 7, a complex mixture was formed from which
the peroxyhemiacetal 23 was isolated in 26% yield.
Apart from the previously observed side products 18 and
19, three new compounds were also obtained: the olefin
20, which was characterized as its methyl ester, and the
seven-membered isomeric lactones 21 and 22 (Scheme
5). The structure of the olefin 20 has been investigated
by spectroscopic methods and seems to proceed from the
peroxyhemiacetal via a radical mechanism initiated by
rupture of the peroxide bond. The lactones 21 and 22
differ only in the stereochemistry at C-2 because the
corresponding sulfones 27 and 28 can be oxidized to the
same ketone 29 (Scheme 6). The structure and stereo-
chemistry of these lactones were confirmed by X-ray
crystallographic analysis26 of a crystalline p-bromoben-
(26) The author has deposited the atomic coordinates for this
structure with the Cambridge Crystallographic Data Centre. The
coordinates can be obtained, upon request, from the Director, Cam-
bridge Crystallographic Data Centre, 12 Union Road, Cambridge, CB2
1EZ, UK.

4700 J . Org. Chem., Vol. 63, No. 14, 1998
Boto et al.
Sch em e 6a
F igu r e 1. Peroxyhemiacetal tautomeric equilibrium.
Sch em e 7a
a
Key: (a) p-TsOH‚H2O, MeOH/CH2Cl2, rt, 24 h, 81% (ca. 1:1).
a
Key: (a) m-CPBA, CH2Cl2, rt, 30-50 min, 89-97%; (b)
p-bromobenzoyl chloride, Py, rt, 24 h, 64%; (c) PCC, CH2Cl2, rt,
The sulfone 13 was studied as its conformationally
locked methyl acetal derivatives 30 and 31 (Scheme 7).
These compounds were obtained in 81% yield (ca. 1:1),
by treatment of the sulfone 13 with MeOH in the
presence of catalytic amounts of p-TsOH. The acetal 30
showed coupling constants at J 2′R,1′R ) 1.3 Hz (eq-ax) and
26 h, 29%; (d) TPAP, NMO, CH2Cl2, rt, 10 min, 38%.
zoate ester derivative 26. The formation of lactones 21
and 22 can be explained by assuming that peroxyhemi-
acetal 23 and its unisolated epimer at C-2 undergo an
intramolecular Baeyer-Villiger rearrangement.27 Al-
though there is some evidence for a stereoelectronic
control in the regioselectivity of the Baeyer-Villiger
reaction,28 and accordingly, the migrating group in this
case should be the secondary center at C-6, only products
coming from the migration of the quaternary center (C-
10) have been detected.29
J 2′R,1′â ) 4.5 Hz (eq-eq), while acetal 31 showed J 2′R,1′â
)
11.1 Hz (ax-ax) and J 2′R,1′R ) 1.8 Hz (ax-eq) as corre-
sponding for the trans- and cis-fused AA′ ring system,
respectively.
Ra d ica l â-F r a gm en ta tion of P er oxyh em ia ceta ls
11, 13, 17, a n d 24. At first, the sulfide 10 was subjected
to our standard reaction conditions for generation of the
alkoxy radical,12 with 1.1-1.5 equiv of DIB and 1 equiv
of I2 at different temperatures (-20, 0, +20, or +40 °C)
and reaction times (15-60 min) while the solution was
irradiated with visible light, but unfortunately, all efforts
to apply this â-fragmentation process failed and an
inseparable mixture of unidentified products was ob-
tained.
In all cases, the γ-hydroperoxy carbonyl sulfides 10,
12, 15, 16, and 23 and sulfones 11, 13, 17, and 24
obtained were in a ring-chain tautomeric equilibrium
displaced far to the side of the cyclic peroxyhemiacetal
grouping as evidenced by their spectroscopic data.30 In
fact, their IR spectra exhibited an absorption for a
tertiary hydroxyl group in the 3578-3595 cm-1 region,
and their 13C NMR spectra do not present the resonance
of a free carbonyl group, but rather a signal correspond-
ing to a hemiacetal carbon at 99-105 ppm (singlet, DEPT
experiment).
Gratifyingly, when the reaction was performed with
the sulfone 11, at ca. 25 °C for 15 min, the dioxolane 32
was obtained in 55% yield (Scheme 8). Purification of
the crude residue containing the acid 32 was better
accomplished by methylation with ethereal diazomethane
and chromatography of the resulting methyl ester 33
(64% overall yield). Dioxolane 32 presents in its IR
spectrum stretches at 3500-2500 and 1728 cm-1 typical
of a carboxylic acid function, but its structure and
stereochemistry were better studied on the methyl ester
derivative 33. Accurate mass and elemental analysis
measurements are in good agreement with the empirical
formula C37H58O6S calculated for this derivative. The
NMR spectra were carefully studied using DEPT, HMBC,
and HMQC experiments to assign carbons and protons.
The observed coupling constants of the signals at δ 4.32
(dddd) and 4.70 (dddd) corresponding to the protons at
C-2â and C-2′â, respectively, do not provide conclusive
evidence to determine the syn or anti stereochemistry of
the disubstituted dioxolane ring. However, a syn relative
stereochemistry could be assigned from ROESY experi-
ments that established a correlation between the C-2 and
C-2′ protons. The structure and relative stereochemistry
of the dioxolane ring of compound 33 have been confirmed
by X-ray crystallographic analysis.26 The five-membered
ring displays an envelope conformation in which the C-2′
1
While the H and 13C NMR spectra for compounds 10,
11, 23, and 24 indicated trans-fused AA′ rings as the sole
structure, compounds 12 and 13 showed major signals
for a cis-fused structure accompanied by minor signals
for a trans-fused one (ca. 9:1, and 4:1, respectively)
(Figure 1). In compounds 15-17, the proportions of the
two isomers are more balanced (trans:cis, ca. 1.5:1, 2.3:
1, and 2.6:1, respectively). These results are in accord
with MMX force-field31 calculations.
(27) Krow, G. R. In Organic Reactions; Paquette, L. A., Ed.; J ohn
Wiley & Sons: New York, 1993; Vol. 43, pp 251-798.
(28) (a) Chandrasekhar, S.; Roy, C. D. Tetrahedron Lett. 1987, 28,
6371-6372. (b) Deslongchamps, P. Stereoelectronic Effects in Organic
Chemistry; Pergamon Press: Oxford, 1983.
(29) The steroidal numeration system is used throughout this
section, although a more correct IUPAC systematic nomenclature has
been used in the Experimental Section and Supporting Information
for steroids with more than one ring opened.
(30) For related ring-chain tautomeric equilibrium of hydroxy
ketones, see: (a) Escale, R.; Verducci, J . Bull. Soc. Chim. Fr. 1974,
1203-1206. (b) Whiting, J . E.; Edward, J . T. Can. J . Chem. 1971, 49,
3799-3806. (c) Cottier, L.; Descotes, G. Bull. Soc. Chim. Fr. 1971,
4557-4562. (d) J ones, P. R. Chem. Rev. 1963, 63, 461-487.
(31) MMX force field as implemented in PCMODEL (v. 4.0), Serena
Software, Bloomington, IN 47402-3076.

Stereospecific Synthesis of 1,2-Dioxolanes
J . Org. Chem., Vol. 63, No. 14, 1998 4701
Sch em e 8: Syn th esis of 1,2-Dioxola n esa
Sch em e 9
matography on deactivated silica gel, and although it
decomposed quickly its structure was fully characterized
by its IR and 1H and 13C NMR spectroscopic data. In
fact, peroxylactone 35 presents in its IR spectrum a
carbon-oxygen stretch at 1770 cm-1 of the peroxylactone
1
group. The H NMR spectrum shows complex signals at
δ 4.25 and 4.75 corresponding to the protons at C-2 and
C-2′, respectively, while in its 13C NMR the signals
corresponding to these carbons appear at δ 19.6 and 84.3,
respectively, assigned by DEPT, HMBC, and HMQC
experiments. When the crude reaction mixture was
treated with sodium methoxide, dioxolane 36 was ob-
tained as the sole product (79% yield).
However, when the fragmentation reaction was per-
formed with peroxyhemiacetal 24, the corresponding
dioxolane 37 was obtained only in moderate yield,
presumably due to the reactivity of the C-radical inter-
mediate.
A plausible mechanism for the formation of dioxolanes
33, 34, 36, and 37 is shown in Scheme 9, exemplified by
dioxolane 36, and involves the in situ generation of the
alkoxy radical V from the corresponding peroxyhemi-
acetal 17. This alkoxy radical undergoes regioselective
C2-C3 bond fragmentation to provide the carbon radical
VI, which abstracts in a stereoselective manner an iodine
atom from the reaction medium to give the 10-membered
iodoperoxylactone 35. The formation of 1,2-dioxolanes
from this medium-sized peroxylactone intermediate sug-
gests the nucleophilic attack of a hydroxide or methoxide
anion on the acyl carbon and then the resulting peroxy-
anion produces intramolecular nucleophilic substitution
of the iodide at C-2 to give 36. A survey of the literature
revealed that there exist examples involving a nucleo-
philic hydroxide ion attack to the acyl carbon of a peroxy
ester. Indeed, the hydrolysis of a peroxy ester to give a
carboxylic acid and a hydroperoxide occurs by this
mechanism.32 As can be observed, a retention of config-
uration by a double inversion has occurred at C-2. Of
particular interest from the mechanistic point of view was
the isolation of the peroxylactone 35 and its further
transformation to the methyl ester 36 by treatment with
methanolic sodium methoxide solution, since it strongly
supports the proposed mechanism for the formation of
dioxolanes. It is also noteworthy that despite the fact
a
Key: (a) DIB, I2, CH2Cl2, hν, 20-30 °C, 15-30 min; (b) CH2N2,
Et2O, 0 °C, 5 min; (c) NaOMe, MeOH, rt, 3.5 h, 79%.
is below the plane formed by the peroxide group and the
two other carbons.
An analogous procedure was used with sulfones 13, 17,
and 24, and the fragmentation proceeded smoothly under
mild conditions, with a temperature below 30 °C and
reaction times no longer than 30 min. When the frag-
mentation reaction was performed with the sulfone 13,
dioxolane 34 was obtained in 66% yield and showed
spectroscopic data analogous to those of compound 33.
The principal difference came from the coupling constants
for C-1′R and C-1′â protons at δ 2.43 and 2.70, respec-
tively. On the other hand, no NOE correlation was
observed between protons at C-2 and C-2′ in the 2D
ROESY spectrum, and hence, 34 must have anti sub-
stituents at C-2 and C-2′ with the S and R configuration,
respectively.
In the case of peroxyhemiacetal 17, the unstable
intermediate 10-membered cyclic peroxylactone 35 was
obtained. This could be isolated by chromatotron chro-
(32) For nucleophilic reaction of peroxy esters see: Sawaki, Y. In
Organic Peroxides; Ando, W., Ed.; J ohn Wiley & Sons: New York, 1992;
p 452.

4702 J . Org. Chem., Vol. 63, No. 14, 1998
Boto et al.
S, 5.64. Found: C, 76.35; H, 10.23; S, 5.36. Peroxyhemiacetal
12 (inseparable mixture, cis-:trans-fused AA′ rings, 9:1):
amorphous; IR 3578, 1698 cm-1; 1H NMR (200 MHz) cis-fused,
δ 0.64 (3H, s), 0.82 (3H, s), 0.86 (6H, d, J ) 6.7 Hz), 0.89 (3H,
d, J ) 7.2 Hz), 2.84 (1H, dd, J ) 13.7, 6.5 Hz), 3.04 (1H, dd, J
) 13.7, 5.9 Hz), 4.47 (1H, dddd, J ) 10.6, 7.1, 5.9, 1.2 Hz),
7.30 (5H, m); 13C NMR (50.3 MHz) cis-fused, δ 11.8 (q), 12.1
(q), 18.7 (q), 21.2 (t), 22.6 (q), 22.8 (q), 23.8 (t), 24.2 (t), 27.8
(t), 28.0 (d), 28.2 (t), 30.5 (t), 31.6 (t), 33.0 (d), 35.2 (d), 35.8
(d), 36.2 (t), 36.7 (t), 38.3 (t), 39.50 (t), 39.54 (s), 39.9 (t), 40.8
(t), 42.0 (d), 42.5 (s), 53.8 (d), 56.2 (d), 56.4 (d), 75.6 (d), 99.9
(s), 126.5 (d), 129.1 (d × 2), 129.7 (d × 2), 135.9 (s); MS m/z
(rel intensity) 550 (M+ - H2O, 6), 535 (15); HRMS calcd for
that the â-fragmentation sequence occurs through a
radical process, total stereospecificity was observed for
the resulting dioxolanes and hence for the iodide inter-
mediates. In conclusion, this methodology is a good
procedure for the preparation of 1,2-dioxolanes in a
stereospecific manner. However, the synthesis of the
peroxyhemiacetal precursors should be improved, and
attempts in this direction are in progress.
Exp er im en ta l Section
Gen er a l Meth od s. Melting points were determined with
a hot-stage apparatus and are uncorrected. Optical rotation
measurements were recorded at room temperature in CHCl3.
IR spectra were recorded in CHCl3 solutions. 1H NMR spectra
were determined at 200, 400, or 500 MHz for CDCl3 solutions
in parts per million from residual CHCl3 (7.26 ppm) as internal
reference. Homonuclear coupling constants (J ) were confirmed
by COSY or single-frequency decoupling experiments. 13C
NMR spectra were recorded at 50.3 or 125.7 MHz and chemical
shifts are reported in ppm from the central peak of CDCl3 (δ
) 77.0) as internal reference. Signal chemical shift and
multiplicity assignments (CH3, q; CH2, t; CH, d; C, s) were
made from DEPT, HETCOR, and HMBC spectra. Mass
spectra were determined at 70 eV. Merck silica gel 60 PF254
and 60 (0.063-0.2 mm) were used for preparative thin-layer
chromatography (TLC) and column chromatography, respec-
tively. Circular layers of 1 mm of Merck silica gel 60 PF254
containing gypsum were used on a Chromatotron for centrifu-
gally assisted chromatography. Commercial reagents and
solvents were analytical grade or were purified by standard
procedures prior to use.33 All reactions involving air- or
moisture-sensitive materials were carried out under a nitrogen
atmosphere. The spray reagent for TLC was vanillin (1 g) in
H2SO4-EtOH (4:1; 200 mL). (Diacetoxyiodo)benzene (DIB)
98% was purchased from Aldrich.
C
36H54O2S 550.3845, found 550.3808. Anal. Calcd for C36H56-
O3S: C, 76.01; H, 9.92; S, 5.64. Found: C, 75.85; H, 10.14; S,
5.82. The 1H and 13C NMR data of the minor isomer (trans-
fused) could not be selected from the spectra of the mixture.
(2S,2′S,3R)-2-[2-Hydr oper oxy-3-(ph en ylsu lfon yl)pr opyl]-
5r-ch olesta n -3-on e 2′,3-P er oxyh em ia ceta l (11). To a solu-
tion of phenylsulfide 10 (114 mg, 0.2 mmol) in CH2Cl2 (6 mL)
was added 85% m-CPBA (103 mg, 0.51 mmol), and the
resulting solution was stirred at room temperature for 45 min.
The reaction mixture was poured into water and extracted
with CH2Cl2. The organic layer was washed with 1% NaOH,
5% hydrochloric acid, and water, dried (Na2SO4), and evapo-
rated. Chromatotron chromatography of the residue (benzene-
EtOAc 97:3) afforded sulfone 11 (117 mg, 96%): mp 168-169
°C (from acetone-n-hexane); [R]D ) +43 (c ) 0.142); IR 3595,
1325, 1151 cm-1; 1H NMR (400 MHz) δ 0.65 (3H, s), 0.84 (3H,
s), 0.85 (6H, d, J ) 5.6 Hz), 0.88 (3H, d, J ) 8.0 Hz), 1.95 (1H,
m), 3.14 (1H, dd, J ) 14.8, 5.1 Hz), 3.32 (1H, dd, J ) 14.8, 6.4
Hz), 4.72 (1H, dddd, J ) 10.3, 6.4, 5.1, 1.5 Hz), 7.56 (2H, dd,
J ) 7.9, 7.9 Hz), 7.66 (1H, dd, J ) 7.4, 7.4 Hz), 7.93 (2H, d, J
) 7.3 Hz);13C NMR (50.3 MHz) δ 12.1 (q), 12.8 (q), 18.7 (q),
21.3 (t), 22.6 (q), 22.8 (q), 23.8 (t), 24.1 (t), 28.0 (d), 28.1 (t),
28.2 (t), 31.3 (t), 31.9 (t), 35.3 (d), 35.8 (d), 36.1 (t), 36.6 (t),
37.0 (s), 37.1 (d), 39.5 (t), 39.9 (t), 40.9 (t), 42.6 (s), 43.3 (d),
53.9 (d), 56.2 (d), 56.3 (d), 59.1 (t), 77.0 (d), 101.4 (s), 128.1 (d
× 2), 129.3 (d × 2), 134.0 (d), 139.5 (s); MS m/z (rel intensity)
582 (M+ - H2O, 6), 385 (100); HRMS calcd for C36H54O4S
582.3743, found 582.3734. Anal. Calcd for C36H56O5S: C,
71.96; H, 9.39; S, 5.34. Found: C, 71.68; H, 9.55; S, 5.54.
(2S,2′R,3R/S)-2-[2-Hyd r op er oxy-3-(p h en ylsu lfon yl)p r o-
p yl]-5r-ch olesta n -3-on e 2′,3-P er oxyh em ia ceta l (13). Sul-
fide 12 (93 mg, 0.164 mmol) in CH2Cl2 (7 mL) was treated with
85% m-CPBA (84 mg, 0.41 mmol) at room temperature for 50
min. Workup as above and chromatotron chromatography of
the residue (benzene-EtOAc 97.5:2.5) gave the sulfone 13
(inseparable mixture, cis-/trans-fused AA′ rings, 4:1) (86.5 mg,
88%): mp 164-166 °C (from acetone-n-pentane); [R]D ) +77
Details of the experimental procedures, physical properties,
and spectroscopic data for compounds 1-7 are included in the
Supporting Information.
Reaction of 2r-(2-P r open yl)-5r-ch olestan -3-on e (3) with
Ben zen eth iol a n d Oxygen . A solution of olefin 3 (500 mg,
1.17 mmol) and benzenethiol (0.5 mL, 4.88 mmol) in acetic
acid (12.5 mL) was treated with a stream of oxygen bubbled
through the reaction mixture, at room temperature, for 45 h.
The reaction was quenched with water and extracted with
CH2Cl2. The organic layer was washed with 2% NaOH, 5%
hydrochloric acid, and water, dried over Na2SO4, and concen-
trated under reduced pressure. Silica gel column chromatog-
raphy of the residue (hexanes-EtOAc 95:5) gave 2R-[3-
(phenylthio)propyl]-5R-cholestan-3-one (8) (69 mg, 11%), 2R-
[2-oxo-3-(phenylthio)propyl]-5R-cholestan-3-one (9) (39 mg,
6%), (2S,2′S,3R)-2-[2′-hydroperoxy-3′-(phenylthio)propyl]-5R-
cholestan-3-one 2′,3-peroxyhemiacetal (10) (187 mg, 28%), and
(2S,2′R,3R/S)-2-[2′-hydroperoxy-3-(phenylthio)propyl]-5R-cho-
lestan-3-one 2′,3-peroxyhemiacetal (12) (167 mg, 25%). Physi-
cal properties and spectroscopic data for side products 8 and
9 are provided in the Supporting Information. Peroxyhemi-
acetal 10: mp 150-151 °C (from n-hexane); [R]D ) -111 (c )
(c ) 0.246); IR 3579, 1307, 1148 cm-1 1H NMR (400 MHz)
;
cis-fused, δ 0.65 (3H, s), 0.81 (3H, s), 0.87 (6H, d, J ) 6.4 Hz),
0.92 (3H, d, J ) 6.3 Hz), 3.12 (1H, dd, J ) 14.8, 7.1 Hz), 3.29
(1H, dd, J ) 14.8, 4.5 Hz), 4.92 (1H, dddd, J ) 10.7, 7.1, 4.5,
1.5 Hz), 7.57 (2H, dd, J ) 8.0, 8.0 Hz), 7.67 (1H, dd, J ) 7.6,
7.6 Hz), 7.94 (2H, d, J ) 7.6 Hz); trans-fused, 0.64 (3H, s),
0.81 (3H,s), 0.86 (6H, d, J ) 8.0 Hz), 0.91 (3H, d, J ) 6.3 Hz),
3.49 (1H, dd, J ) 14.5, 5.8 Hz), 3.99 (1H, dd, J ) 14.5, 6.1
Hz), 4.76 (1H, dddd, J ) 6.1, 5.8, 4.8, 1.8 Hz), 7.57 (2H, dd, J
) 8.0, 8.0 Hz), 7.67 (1H, dd, J ) 7.6, 7.6 Hz), 7.94 (2H, d, J )
7.6 Hz); 13C NMR (50.3 MHz) cis-fused, δ 11.7 (q), 12.0 (q),
18.7 (q), 21.2 (t), 22.5 (q), 22.8 (q), 23.8 (t), 24.2 (t), 27.7 (t),
28.0 (d), 28.2 (t), 30.9 (t), 31.6 (t), 32.6 (d), 35.2 (d), 35.8 (d),
36.1 (t), 36.1 (s), 38.5 (t), 39.5 (t), 39.9 (t), 40.5 (t), 42.0 (d),
42.5 (s), 53.7 (d), 56.2 (d), 56.3 (d), 59.4 (t) 71.4 (d), 99.8 (s),
128.1 (d × 2), 129.2 (d × 2), 134.0 (d), 139.8 (s); trans-fused,
12.0 (q), 12.9 (q), 18.7 (q), 21.2 (t), 22.5 (q), 22.8 (q), 23.8 (t),
24.1 (t), 28.0 (d), 28.1 (t), 28.4 (t), 31.7 (t), 31.8 (t), 32.6 (d),
35.3 (d), 35.7 (d), 36.8 (t), 37.1 (s), 38.5 (t), 39.5 (t), 39.8 (t),
40.6 (t), 42.6 (s), 43.3 (d), 53.9 (d), 56.2 (d), 56.3 (d), 57.4 (t),
75.0 (d), 101.8 (s), 128.0 (d × 2), 129.2 (d × 2), 133.9 (d), 139.6
(s); MS m/z (rel intensity) 600 (M+, <1), 582 (15), 141 (100);
HRMS calcd for C36H54O4S 582.3743, found 582.3748. Anal.
Calcd for C36H56O5S: C, 71.96; H, 9.39; S, 5.34. Found: C,
71.77; H, 9.16; S, 5.49.
1
0.166); IR 3579, 1610 cm-1; H NMR (200 MHz) δ 0.64 (3H,
s), 0.84 (3H, s), 0.85 (6H, d, J ) 6.5 Hz), 0.88 (3H, d, J ) 6.4
Hz), 2.85 (1H, dd, J ) 13.8, 7.0 Hz), 3.07 (1H, dd, J ) 13.8,
5.5 Hz), 4.37 (1H, dddd, J ) 10.3, 7.0, 5.5, 2.1 Hz), 7.30 (5H,
m); 13C NMR (50.3 MHz) δ 12.0 (q), 12.8 (q), 18.7 (q), 21.3 (t),
22.6 (q), 22.8 (q), 23.8 (t), 24.2 (t), 28.0 (d), 28.15 (t), 28.22 (t),
30.7 (t), 31.9 (t), 35.3 (d), 35.8 (d), 36.2 (t), 36.3 (t), 36.5 (t),
37.0 (s), 37.1 (d), 39.5 (t), 40.0 (t), 41.2 (t), 42.6 (s), 43.3 (d),
54.0 (d), 56.2 (d), 56.4 (d), 81.0 (d), 101.3 (s), 126.5 (d), 129.1
(d × 2), 129.6 (d × 2), 135.6 (s); MS m/z (rel intensity) 550
(M+ - H2O, 10), 534 (50); HRMS calcd for C36H54O2S 550.3845,
found 550.3844. Anal. Calcd for C36H56O3S: C, 76.01; H, 9.92;
(33) Perrin, D. D.; Armarego, W. L. F. Purification of Laboratory
Chemicals, 3rd ed.; Pergamon Press: New York, 1988.

Stereospecific Synthesis of 1,2-Dioxolanes
J . Org. Chem., Vol. 63, No. 14, 1998 4703
Reaction of 2â-(2-P r open yl)-5r-ch olestan -3-on e (2) with
Ben zen eth iol a n d Oxygen . A solution of alkene 2 (350 mg,
0.82 mmol) in acetic acid (15 mL) was treated with PhSH (0.4
mL, 3.9 mmol) and oxygen for 48 h as described previously.
Workup and chromatotron chromatography of the residue
(hexanes-EtOAc 49:1-7:3) afforded (2R,2′S,3R/S)-2-[2′-hy-
droperoxy-3′-(phenylthio)propyl]-5R-cholestan-3-one 2′,3-per-
oxyhemiacetal (15) (28 mg, 6%), 2â-[3-(phenylthio)propyl]-5R-
cholestan-3-one (14) (9 mg, 2%), peroxyhemiacetal 10 (37 mg,
8%), (2R,2′R,3R/S)-2-[2′-hydroperoxy-3-(phenylthio)propyl]-5R-
cholestan-3-one 2′,3-peroxyhemiacetal (16) (80 mg, 17%), and
peroxyhemiacetal 12 (19 mg, 4%). Physical properties and
spectrocopic data for the side product 14 are provided in the
Supporting Information. Peroxyhemiacetal 15 (inseparable
mixture, trans-/cis-fused AA′ rings, 1.5:1): amorphous; IR
3620, 1584 cm-1; 1H NMR (200 MHz) trans-fused, δ 0.64 (3H,
s), 0.74 (3H, s), 0.87 (6H, d, J ) 6.7 Hz), 0.92 (3H, d, J ) 6.4
Hz), 3.12 (1H, dd, J ) 13.2, 7.2 Hz), 3.36 (1H, dd, J ) 13.2,
5.0 Hz), 4.62 (1H, m), 7.35 (5H, m); cis-fused, 0.63 (3H, s), 0.69
(3H, s), 0.87 (6H, d, J ) 6.7 Hz), 0.91 (3H, d, J ) 6.4 Hz), 3.37
(1H, dd, J ) 13.2, 6.6 Hz), 3.63 (1H, dd, J ) 13.2, 7.0 Hz),
4.44 (1H, m), 7.35 (5H, m); 13C NMR (50.3 MHz) trans-fused,
δ 10.9 (q), 12.0 (q), 18.6 (q), 21.0 (t), 22.5 (q), 22.8 (q), 23.8 (t),
24.2 (t), 27.9 (t), 28.0 (d), 28.2 (t), 31.6 (t), 35.2 (d), 35.8 (d),
36.1 (t), 36.2 (s), 37.5 (t), 39.3 (t), 39.5 (t × 2), 39.9 (t), 41.2
(d), 41.5 (d), 42.4 (s), 44.7 (t), 53.4 (d), 56.2 (d), 56.4 (d), 76.2
(d), 98.0 (s), 126.1 (d), 128.0 (d), 128.6 (d), 128.9 (d), 129.3 (d),
132.4 (s); cis-fused, 11.0 (q), 12.0 (q), 18.6 (q), 21.0 (t), 22.5
(q), 22.8 (q), 23.8 (t), 24.2 (t), 27.9 (t), 28.0 (d), 28.2 (t), 31.6
(t), 35.2 (d), 35.5 (s), 35.8 (d), 36.1 (t), 39.0 (t), 39.4 (t × 2),
39.6 (t), 40.0 (t), 41.3 (d), 42.0 (t), 42.3 (d), 42.4 (s), 53.4 (d),
56.2 (d), 56.4 (d), 78.5 (d), 97.9 (s), 126.0 (d), 128.5 (d × 2),
128.9 (d), 129.1 (d), 132.8 (s); MS m/z (rel intensity) 435 (M+
- H2O - CH3, 5), 109 (100). Anal. Calcd for C36H56O3S: C,
76.01; H, 9.92; S, 5.64. Found: C, 76.22; H, 9.74; S, 5.87.
Peroxyhemiacetal 16 (inseparable mixture, trans-/cis-fused
fused, δ 12.1 (q), 14.8 (q), 18.6 (q), 21.1 (t), 22.5 (q), 22.8 (q),
23.8 (t), 24.1 (t), 28.0 (t), 28.0 (d), 28.2 (t), 31.6 (d), 33.3 (d),
34.0 (t), 35.0 (d), 35.7 (d), 35.9 (s), 36.1 (t), 37.0 (d), 39.5 (t),
39.8 (t), 39.9 (t), 41.89 (d), 42.6 (s), 55.2 (d), 56.2 (d × 2), 60.4
(t), 75.3 (d), 105.0 (s), 128.0 (d × 2), 129.3 (d × 2), 133.8 (d),
139.8 (s); cis-fused, 12.1 (q), 15.3 (q), 18.6 (q), 21.2 (t), 22.5
(q), 22.8 (q), 23.8 (t), 24.1 (t), 28.0 (d), 28.0 (t), 28.2 (t), 32.0
(t), 33.3 (t), 34.4 (t), 35.1 (d), 35.7 (d), 35.9 (s), 36.1 (t), 37.0
(d), 39.5 (t), 39.8 (t), 39.9 (t), 41.9 (d), 42.5 (s), 56.2 (d × 2),
55.2 (d), 60.0 (t), 73.6 (t), 104.2 (s), 128.1 (d × 2), 129.4 (d ×
2), 134.0 (d), 139.3 (s); MS m/z (rel intensity) 566 (M+ - H2O2,
12), 398 (66). Anal. Calcd for C36H56O5S: C, 71.96; H, 9.39;,
5.34. Found: C, 71.88; H, 9.48; S, 5.16.
Rea ction of 4-Nor -3,4-secoch olest-2-en -5-on e (7) w ith
Ben zen eth iol a n d Oxygen . To a solution of the olefin 7 (117
mg, 0.31 mmol) in AcOH (5.4 mL) was added benzenethiol
(PhSH) (0.152 mL, 1.29 mmol), and then a stream of oxygen
was bubbled through the resulting mixture at room temper-
ature for 36 h. The reaction mixture was poured into water
and extracted with CH2Cl2. The organic layer was washed
with 1% NaOH, 5% hydrochloric acid (5 mL), and water, dried
(Na2SO4), and evaporated. Chromatotron chromatography of
the residue (hexanes-EtOAc 100:0 to 1:1) gave 3-(phenylthio)-
4-nor-3,4-secocholestan-5-one (18) (11 mg, 7%), 3-(phenylthio)-
4-nor-3,4-secocholestane-2,5-dione (19) (30 mg, 19%), (2S,5R)-
hydroperoxy-3-(phenylthio)-4-nor-3,4-secocholestan-5-one 2,5-
peroxyhemiacetal (23) (42 mg, 26%), and a mixture that after
methylation was resolved by chromatotron chromatography
(hexanes-EtOAc 4:1) in the olefin 20 (11 mg, 9%), (3R,3aR,-
5aS,6R,10aS,10bS,2′S,1′′R)-(21) (13 mg, 8%), and (3R,3aR,-
5aS,6R,10aS,10bS,2′R,1′′R)-3-(1′′,5′′-dimethylhexyl)-6-[2′-hy-
droxy-3′-(phenylthio)propyl]-3a,6-dimethyl-dodecahydro-7-oxa-
cyclohepta[e]inden-8-one (22) (5 mg, 3%). Physical properties
and spectroscopic data for side products 18-22 are included
in the Supporting Information. Peroxyhemiacetal 23: amor-
phous; IR 3576, 1583 cm-1; 1H NMR (200 MHz) δ 0.65 (3H, s),
0.87 (6H, d, J ) 6.5 Hz), 0.90 (3H, d, J ) 8.3 Hz), 1.00 (3H, s),
2.77 (1H, dd, J ) 13.5, 7.1 Hz), 3.05 (1H, dd, J ) 13.5, 5.4
Hz), 4.48 (1H, dddd, J ) 11.4, 7.1, 5.4, 1.3 Hz), 7.36 (5H, m);
13C NMR (50.3 MHz) δ 11.9 (q), 18.0 (q), 18.6 (q), 21.4 (t), 22.5
(q), 22.8 (q), 23.8 (t), 24.1 (t), 27.1 (t), 28.0 (d), 28.2 (t), 31.5
(t), 34.0 (t), 34.6 (d), 35.7 (d), 36.1 (t), 36.6 (t), 38.9 (s), 39.5 (t),
39.7 (t), 42.3 (s), 43.1 (d), 55.9 (d), 56.1 (d), 75.9 (d), 102.4 (s),
126.7 (d), 129.0 (d × 2), 130.2 (d × 2), 135.4 (s); MS m/z (rel
intensity) 496 (M+ - H2O, <1), 123 (100). Anal. Calcd for
AA′, 2.3:1): amorphous; IR 3579, 1468 cm-1 1H NMR (200
;
MHz) trans-fused, δ 0.66 (3H, s), 0.88 (6H, d, J ) 6.7 Hz), 0.91
(3H, d, J ) 6.6 Hz), 3.03 (1H, dd, J ) 13.5, 7.1 Hz), 3.29 (1H,
dd, J ) 13.5, 6.1 Hz), 4.12 (1H, m), 7.30 (5H, m); cis-fused,
0.66 (3H, s), 0.72 (3H, s), 0.88 (6H, d, J ) 6.7 Hz), 0.91 (3H, d,
J ) 6.6 Hz), 2.89 (1H, dd, J ) 13.5, 8.1 Hz), 3.07 (1H, dd, J )
13.3, 5.2 Hz), 4.49 (1H, m), 7.30 (5H, m); 13C NMR (50.3 MHz)
trans-fused, δ 12.1 (q), 14.96 (q), 18.6 (q), 21.1 (t), 22.5 (q),
22.8 (q), 23.8 (t), 24.1 (t), 28.0 (d), 28.2 (t), 31.7 (t), 33.5 (d),
33.9 (t), 35.0 (d), 35.8 (d), 35.9 (s), 36.1 (t), 37.7 (d), 37.8 (t),
39.5 (t × 2), 40.0 (t), 40.2 (t), 42.0 (d), 42.6 (s), 55.2 (d), 56.2 (d
× 2), 80.6 (d), 104.8 (s), 128.3 (d), 129.0 (d × 2), 129.5 (d × 2),
135.7 (s); cis-fused, 12.1 (q), 15.0 (q), 18.6 (q), 21.1 (t), 22.5
(q), 22.8 (q), 23.8 (t), 24.1 (t), 27.97 (d), 28.03 (t), 31.2 (t), 34.1
(t), 34.4 (t), 35.1 (d), 35.75 (d), 35.82 (s), 36.1 (t), 37.7 (d), 37.8
(t), 39.5 (t × 2), 39.8 (t), 40.2 (t), 41.7 (d), 42.6 (s), 55.2 (d),
56.2 (d × 2), 77.6 (d), 104.2 (s), 128.5 (d), 128.2 (d × 2), 129.0
(d × 2), 135.4 (s); MS m/z (rel intensity) 535 (M+ - H2O -
CH3, 5), 109 (100). Anal. Calcd for C36H56O3S: C, 76.01; H,
9.92; S, 5.64. Found: C, 76.24; H, 9.79; S, 5.53.
C
32H50O3S: C, 74.66; H, 9.79; S, 6.23. Found: C, 74.75; H,
9.65; S, 6.05.
(2S,5R)-[2-Hyd r op er oxy-3-(p h en ylsu lfon yl)]-4-n or -3,4-
secoch olesta n -5-on e 2,5-P er oxyh em ia ceta l (24). A solu-
tion of sulfide 23 (31 mg, 0.06 mmol) in CH2Cl2 (2 mL) was
treated with 55% m-CPBA (50 mg, 0.16 mmol) at room
temperature for 1 h. Workup as previously described and
chromatotron chromatography (hexanes-EtOAc 7:3) afforded
the sulfone 24 (31 mg, 94%): amorphous; IR 3577, 1308, 1154
1
cm-1; H NMR (500 MHz) δ 0.66 (3H, s), 0.87 (3H, d, J ) 6.4
Hz), 0.88 (3H, d, J ) 6.4 Hz), 0.93 (3H, d, J ) 6.4 Hz), 0.98
(3H, s), 3.11 (1H, dd, J ) 14.8, 5.6 Hz), 3.26 (1H, dd, J ) 14.8,
6.0 Hz), 4.85 (1H, dddd, J ) 11.6, 6.0, 5.7, 1.9 Hz), (3H, s),
7.57 (2H, dd, J ) 8.0, 8.0 Hz), 7.66 (1H, dd, J ) 7.2, 7.2 Hz),
7.92 (2H, d, J ) 7.2 Hz); 13C NMR (50.3 MHz) δ 11.9 (q), 17.9
(q), 18.6 (q), 21.4 (t), 22.5 (q), 22.8 (q), 23.8 (t), 24.1 (t), 27.0
(t), 28.0 (d), 28.2 (t), 31.8 (t), 34.57 (t), 34.58 (d), 35.7 (d), 36.1
(t), 38.7 (s), 39.5 (t), 39.7 (t), 42.3 (s), 43.0 (d), 55.8 (d), 56.1
(d), 59.1 (t), 71.8 (d), 102.5 (s), 128.0 (d × 2), 129.3 (d × 2),
134.0 (d), 139.6 (s); MS m/z (rel intensity) 546 (M+, <1), 528
(4), 77 (100). Anal. Calcd for C32H50O5S: C, 70.29; H, 9.22;
S, 5.86. Found: C, 70.47; H, 9.37; S, 5.53.
(2R,2′R,3R/S)-2-[2′-Hydr oper oxy-3′-(ph en ylsu lfon yl)pr o-
p yl]-5r-ch olesta n -3-on e 2′,3-P er oxyh em ia ceta l (17).
A
solution of 16 (33 mg, 0.058 mmol) in CH2Cl2 (3 mL) was
treated with 55% m-CPBA (33 mg, 0.11 mmol) for 1 h as
described previously. Chromatotron chromatography of the
residue (hexanes-EtOAc 4:1) afforded sulfone 17 (32 mg, 92%)
(inseparable mixture, trans-/cis-fused AA′, 2.6:1): mp 140-
144 °C (from acetone-n-hexane); [R]D ) -36 (c ) 0.22); IR
3579, 1308, 1152 cm-1; 1H NMR (500 MHz) trans-fused, δ 0.65
(3H, s), 0.82 (3H, s), 0.86 (3H, d, J ) 6.6 Hz), 0.87 (3H, d, J )
6.6 Hz), 0.90 (3H, d, J ) 6.5 Hz), 3.31 (1H, dd, J ) 14.4, 5.2
Hz), 3.66 (1H, dd, J ) 14.5, 6.6 Hz), 4.58 (1H, dddd, J ) 9.3,
6.8, 6.6, 5.2 Hz), 7.58 (2H, d, J ) 7.5, 6.7 Hz), 7.66 (1H, dd, J
) 7.6, 7.6 Hz), 7.92 (2H, J ) 7.3 Hz); cis-fused, 0.66 (3H, s),
0.82 (3H, s), 0.86 (3H, d, J ) 6.6 Hz), 0.87 (3H, d, J ) 6.6 Hz),
0.91 (3H, d, J ) 6.5 Hz), 3.29 (1H, dd, J ) 14.3, 8.9 Hz), 3.40
(1H, dd, J ) 14.6, 4.8 Hz), 4.75 (1H, dddd, J ) 11.7, 8.9, 4.8,
4.6 Hz), 7.58 (2H, dd, J ) 7.5, 7.5 Hz), 7.66 (1H, dd, J ) 7.6,
7.6 Hz), 7.92 (2H, d, J ) 7.3 Hz); 13C NMR (50.3 MHz) trans-
Details of the experimental procedures, physical properties,
and spectroscopic data for compounds 25-29 are included in
the Supporting Information.
Rea ction of P er oxyh em ia ceta l 13 w ith Meth a n ol-p-
Tolu en esu lfon ic Acid . To a solution of sulfone 13 (50 mg,
0.084 mmol) in MeOH-CH2Cl2 (5:2, 14 mL) was added
p-TsOH‚H2O (5 mg, 0.026 mmol), and the resulting mixture
stirred at room temperature for 24 h. The solvent was

4704 J . Org. Chem., Vol. 63, No. 14, 1998
Boto et al.
evaporated under reduced pressure and the residue dissolved
in CH2Cl2 (5 mL) and then treated with Dowex 1-X8 (20 mg)
at room temperature for 30 min. The solid phase was removed
by filtration, the solvent evaporated off, and the residue
purified by chromatotron chromatography (benzene-EtOAc
99.4:0.6), giving (2S,2′R)-3R-methoxy- (30) (19 mg, 37%) and
(2S,2′R)-3â-methoxy-2-[2′-hydroperoxy-3′-(phenylsulfonyl)pro-
pyl]-5R-cholestan-3-one 2′,3-peroxyhemiacetal (31) (23 mg,
44%). Compound 30: mp 174-176 °C (from CHCl3-MeOH);
[R]D ) -155 (c ) 0.12); IR 1307, 1151 cm-1; 1H NMR (200 MHz)
δ 0.6 (3H, s), 0.84 (3H, s), 0.86 (6H, d, J ) 6.8 Hz), 0.89 (3H,
d, J ) 6.3 Hz), 2.22 (1H, ddd, J ) 13.0, 12.9, 5.4 Hz), 3.19
(3H, s), 3.49 (1H, dd, J ) 14.5, 5.5 Hz), 3.95 (1H, dd, J ) 14.5,
6.1 Hz), 4.69 (1H, dddd, J ) 5.9, 5.4, 4.5, 1.3 Hz), 7.50 (2H,
m), 7.95 (2H, m); 13C NMR (50.3 MHz) δ 12.1 (q), 15.2 (q), 18.6
(q), 21.3 (t), 22.6 (q), 22.8 (q), 23.8 (t), 24.1 (t), 27.9 (t), 28.0
(d), 28.2 (t × 2), 30.6 (t), 32.0 (t), 32.2 (d), 35.3 (d), 35.8 (d),
36.2 (t), 37.0 (s), 39.5 (t), 39.9 (t), 40.4 (d), 42.6 (s), 42.9 (d),
47.8 (q), 54.0 (d), 56.2 (d), 56.3 (t), 57.9 (t), 74.7 (d), 103.5 (s),
128.1 (d × 2), 129.3 (d × 2), 133.8 (d), 139.6 (s); MS m/z (rel
intensity) 614 (M+, 1), 389 (100); HRMS calcd for C37H58O5S
614.4005, found 614.4000. Anal. Calcd for C37H58O5S: C,
72.27; H, 9.51; S, 5.21. Found: C, 72.09; H, 9.75; S, 5.14.
Compound 31: mp 148-149 °C (from MeOH); [R]D ) +112 (c
dddd, J ) 11.2, 6.1, 6.1, 6.1 Hz), 7.59 (2H, dd, J ) 7.9, 7.9
Hz), 7.68 (1H, dd, J ) 7.5, 7.5 Hz), 7.92 (2H, d, J ) 7.5 Hz);
13C NMR (50.3 MHz) δ 12.0 (q), 15.8 (q), 18.7 (q), 21.8 (t), 22.6
(q), 22.8 (q), 23.8 (t), 24.2 (t), 28.0 (d), 28.2 (t), 31.3 (t), 35.6
(d), 35.8 (d), 36.0 (t), 36.2 (t), 38.4 (s), 39.1 (t), 39.5 (t × 2),
39.8 (t), 40.1 (d), 42.3 (s), 47.8 (t), 48.6 (d), 51.6 (q), 56.2 (d),
56.4 (d), 60.9 (t), 74.5 (d), 77.6 (d), 128.1 (d × 2), 129.3 (d × 2),
133.9 (d), 139.7 (s), 174.1 (s); MS m/z (rel intensity) 630 (M+,
56), 612 (6), 388 (100); HRMS calcd for C37H58O6S 630.3954,
found 630.3958. Anal. Calcd for C37H58O6S: C, 70.44; H, 9.27;
S, 5.08. Found: C, 70.54; H, 9.43; S, 4.91. Conducting the
reaction as before and then treating the crude residue contain-
ing the acid 32 with ethereal CH2N2 at 0 °C for 5 min followed
by purification gave methyl ester 33 in 64% yield.
Rea ction of P er oxyh em ia ceta l 13 w ith (Dia cetoxy-
iod o)ben zen e-Iod in e. A solution of 13 (25 mg, 0.042 mmol)
in CH2Cl2 (4.5 mL) treated with DIB (37 mg, 0.084 mmol) and
I2 (11 mg, 0.042 mmol) was irradiated at 26-28 °C, for 15 min,
as described previously. After workup, the residue was
dissolved in ether (2 mL) and treated at 0 °C with ethereal
CH2N2. After 5 min, the solution was evaporated and the
residue purified by chromatotron chromatography (hexanes-
EtOAc 4:1), giving dioxolane 34 (18 mg, 66%): mp 128-130
°C (from EtOAc-n-pentane); [R]D ) +9 (c ) 0.10); IR 1729,
1309, 1150 cm-1; 1H NMR (400 MHz) δ 0.63 (3H, s), 0.72 (3H,
s), 0.87 (3H, d, J ) 6.6 Hz), 0.88 (3H, d, J ) 6.6 Hz), 0.90 (3H,
d, J ) 6.5 Hz), 1.95 (1H, d, J ) 14.4 Hz), 2.31 (1H, dd, J )
14.4, 2.1 Hz), 2.43 (1H, ddd, J ) 13.5, 7.9, 6.2 Hz), 2.70 (1H,
ddd, J ) 11.9, 7.3, 4.0 Hz), 3.28 (1H, dd, J ) 14.2, 6.7 Hz),
3.50 (2H, dd, J ) 14.2, 5.6 Hz), 3.68 (3H, s), 4.43 (1H, dddd, J
) 9.3, 9.3, 3.2, 0 Hz), 4.70 (1H, dddd, J ) 12.3, 12.3, 6.3, 6.3
Hz), 7.59 (2H, dd, J ) 7.6, 7.6, 1.4 Hz), 7.67 (1H, dd, J ) 7.3,
7.3 Hz), 7.93 (2H, d, J ) 8.1 Hz); 13C NMR (50.3 MHz) δ 12.0
(q), 15.8 (q), 18.6 (q), 21.7 (t), 22.6 (q), 22.9 (q), 23.8 (t), 24.1
(t), 28.0 (d), 28.2 (t × 2), 31.3 (t), 35.4 (d), 35.7 (d), 36.0 (t),
36.1 (t), 38.5 (s), 39.5 (t), 39.7 (t), 40.0 (d), 40.1 (t), 42.3 (s),
47.4 (t), 48.6 (d), 51.7 (q), 56.1 (d), 56.4 (d), 59.5 (t), 74.0 (d),
76.9 (d), 128.1 (d × 2), 129.4 (d × 2), 134.0 (d), 139.4 (s), 174.3
(s); MS m/z (rel intensity) 631 (M+ + 1, 17), 389 (100); HRMS
calcd for C37H58O6S 630.3954, found 630.3955. Anal. Calcd
for C37H58O6S: C, 70.44; H, 9.27; S, 5.08. Found: C, 70.47;
H, 9.31; S, 4.83.
1
) 0.14); IR 1308, 1147 cm-1; H NMR (200 MHz) δ 0.64 (3H,
s), 0.78 (3H, s), 0.86 (6H, d, J ) 6.3 Hz), 0.92 (3H, d, J ) 6.4
Hz), 2.13 (1H, ddd, J ) 13.2, 13.1, 5.2 Hz), 3.07 (1H, dd, J )
14.7, 4.8 Hz), 3.17 (3H, s), 3.26 (1H, dd, J ) 14.7, 6.7 Hz),
4.89 (1H, dddd, J ) 11.1, 6.4, 4.8, 1.8 Hz), 7.61 (3H, m), 7.95
(2H, m); 13C NMR (50.3 MHz) δ 11.7 (q), 12.1 (q), 18.7 (q), 21.1
(t), 22.6 (q), 22.8 (q), 23.8 (t), 24.2 (t), 28.0 (d), 28.1 (t), 28.2
(t), 31.0 (t), 31.7 (t), 32.3 (d), 34.1 (t), 35.2 (d), 35.8 (t), 35.9 (s),
36.2 (t), 39.5 (t), 39.8 (t), 40.4 (t), 41.9 (d), 42.5 (s), 48.1 (s),
53.7 (d), 56.2 (d), 56.3 (d), 59.6 (t), 70.8 (d), 101.6 (s), 128.1 (d
× 2), 129.2 (d × 2), 133.8 (d), 139.9 (s); MS m/z (rel intensity)
614 (M+, <1), 389 (100); HRMS calcd for C37H58O5S 614.4005,
found 614.3996. Anal. Calcd for C37H58O5S: C, 72.27; H, 9.51;
S, 5.21. Found: C, 72.19; H, 9.54; S, 5.26.
Rea ction of P er oxyh em ia ceta l 11 w ith (Dia cetoxy-
iod o)ben zen e-Iod in e. A solution of peroxyhemiacetal 11
(20 mg, 0.033 mmol) in CH2Cl2 (10 mL) containing (diacetoxy-
iodo)benzene (DIB) (43 mg, 0.12 mmol) and iodine (16.2 mg,
0.06 mmol) was irradiated with two 80 W tungsten-filament
lamps at 24-28 °C for 15 min. The reaction mixture was then
poured into water and extracted with CH2Cl2. The organic
layer was washed with aqueous saturated sodium thiosulfate,
dried, and concentrated in vacuo. Chromatotron chromatog-
raphy of the residue (hexanes-EtOAc 1:1) yielded compound
32 (23 mg, 55%): amorphous; IR 3500-2500, 1728, 1321, 1151
Rea ction of P er oxyh em ia ceta l 17 w ith (Dia cetoxy-
iod o)ben zen e-Iod in e. A solution of 17 (20 mg, 0.033 mmol)
in CH2Cl2 (3 mL) was treated with DIB (20 mg, 0.067 mmol)
and I2 (13 mg, 0.051 mmol). The mixture was irradiated as
previously at 22-25 °C for 25 min. After usual workup and
chromatotron chromatography (hexanes-EtOAc 4:1), peroxy-
lactone 35 (8.5 mg, 35%) was obtained: amorphous; IR 1770,
1309, 1153 cm-1; 1H NMR (500 MHz) δ 0.66 (3H, s), 0.70 (3H,
s), 0.87 (3H, d, J ) 6.6 Hz), 0.88 (3H, d, J ) 6.6 Hz), 0.93 (3H,
d, J ) 6.5 Hz), 1.67 (1H, dd, J ) 13.1, 3.3 Hz), 2.35 (1H, dd, J
) 17.4, 5.0 Hz), 2.50 (1H, ddd, J ) 15.6, 11.1, 11.0 Hz), 2.82
(1H, d, J ) 12.0 Hz) 2.99 (1H, dd, J ) 15.8, 1.4 Hz), 3.24 (1H,
dd, J ) 14.2, 8.5 Hz), 3.60 (1H, dd, J ) 14.2, 2.2 Hz), 4.25
(1H, m), 4.75 (1H, dddd, J ) 8.1, 8.1, 8.1, 0 Hz), 7.59 (2H, dd,
J ) 7.9, 7.9 Hz), 7.68 (1H, dd, J ) 7.5, 7.5 Hz), 7.92 (2H, d, J
) 8.1 Hz); 13C NMR (50.3 MHz) δ 12.5 (q), 15.3 (q), 18.6 (q),
19.6 (d), 22.6 (q), 22.8 (q), 23.4 (t), 23.8 (t), 24.1 (t), 28.0 (d),
28.3 (t), 29.6 (t), 30.6 (t), 35.7 (d), 35.8 (d), 36.1 (t × 2), 38.4
(d), 39.4 (t), 39.5 (t × 2), 41.9 (s), 42.4 (s), 46.2 (d), 48.9 (t),
56.1 (d), 56.6 (d), 58.3 (t), 84.3 (d), 127.9 (d × 2), 129.6 (d × 2),
134.3 (d), 139.5 (s), 175.2 (s). Anal. Calcd for C36H55IO5S: C,
59.49; H, 7.63; S, 4.41. Found: C, 59.22; H, 7.78; S, 4.75.
Rea ction of th e P er oxyla cton e 35 w ith Sod iu m Meth -
oxid e. A solution of peroxylactone 35 (5.2 mg, 0.007 mmol)
in MeOH (0.5 mL) was treated with NaOMe (0.5 mg, 0.009
mmol) at room temperature for 3.5 h and then poured into
5% aqueous HCl and extracted with CH2Cl2. The organic layer
was dried and evaporated in the usual way, and the residue
dissolved in ether (0.5 mL) was treated with excess of ethereal
CH2N2. After 30 min, the solution was evaporated and the
residue purified by chromatotron chromatography (benzene-
EtOAc 97:3), giving the methyl ester 36 (3.4 mg, 79%):
cm-1 1H NMR (200 MHz) δ 0.62 (3H, s), 0.72 (3H, s), 0.86
;
(6H, d, J ) 6.6 Hz), 0.89 (3H, d, J ) 5.9 Hz), 2.09 (1H, d, J )
12.2 Hz), 2.38 (1H, d, J ) 12.7 Hz), 3.04 (1H, ddd, J ) 12.4,
7.5, 7.5 Hz), 3.27 (1H, dd, J ) 14.3, 6.2 Hz), 3.58 (1H, dd, J )
14.2, 6.3 Hz), 4.32 (1H, m), 4.70 (1H, m), 7.61 (3H, m), 7.92
(2H, m); 13C NMR (50.3 MHz) δ 12.0 (q), 15.8 (q), 18.6 (q), 21.8
(t), 22.6 (q), 22.8 (q), 23.8 (t), 24.1 (t), 28.0 (d), 28.2 (t), 31.2
(t), 35.5 (d), 35.7 (d), 35.9 (t), 36.1 (t), 38.3 (s), 39.0 (t), 39.5 (t
× 2), 39.7 (t), 39.9 (d), 42.2 (s), 47.7 (t), 48.5 (d), 56.1 (d), 56.3
(d), 60.6 (t), 74.5 (d), 77.7 (d), 128.1 (d × 2), 129.4 (d × 2),
134.0 (d), 139.6 (s), 179.0 (s); MS m/z (rel intensity) 388 (M+
- C10H12O4S, 4), 77 (100); HRMS calcd for C26H44O2 388.3342,
found 388.3350. Anal. Calcd for C36H56O6S: C, 70.09; H, 9.15;
S, 5.20. Found: C, 70.24; H, 9.22; S, 4.98. Compound 32 (18
mg, 0.028 mmol) in ether (1 mL) was treated with ethereal
CH2N2 at 0 °C for 5 min, and then the solvent was evaporated
and the residue purified by chromatotron chromatography
(hexanes-EtOAc 4:1) yielding methyl ester 33 (18 mg, 98%):
mp 135-136 °C (from acetone-n-hexane); [R]D ) +67 (c )
1
0.164); IR 1739, 1322, 1155 cm-1; H NMR (500 MHz) δ 0.62
(3H, s), 0.72 (3H, s), 0.87 (3H, d, J ) 6.6 Hz), 0.88 (3H, d, J )
6.6 Hz), 0.90 (3H, d, J ) 6.5 Hz), 1.92 (1H, dd, J ) 14.4, 1.1
Hz), 2.07 (1H, ddd, J ) 12.9, 8.2, 4.9 Hz), 2.32 (1H, dd, J )
14.4, 2.3 Hz), 3.04 (1H, ddd, J ) 12.4, 7.5, 7.5 Hz), 3.26 (1H,
dd, J ) 14.3, 6.2 Hz), 3.59 (1H, dd, J ) 14.3, 6.2 Hz), 3.67
(3H, s), 4.32 (1H, dddd, J ) 7.5, 7.5, 7.5, 3.5 Hz), 4.70 (1H,
1
amorphous; IR 1728, 1308, 1150 cm-1; H NMR (500 MHz) δ

Stereospecific Synthesis of 1,2-Dioxolanes
J . Org. Chem., Vol. 63, No. 14, 1998 4705
0.64 (3H, s), 0.73 (3H, s), 0.86 (3H, d, J ) 6.6 Hz), 0.87 (3H, d,
J ) 6.6 Hz), 0.92 (3H, d, J ) 6.6 Hz), 1.74 (1H, dd, J ) 15.6,
3.3 Hz), 1.86 (1H, dd, J ) 11.2, 1.7 Hz), 1.94 (1H, m), 2.09
(1H, ddd, J ) 12.5, 8.2, 5.3 Hz), 2.42 (1H, d, J ) 11.8 Hz),
3.00 (1H, ddd, J ) 12.3, 7.1, 7.1 Hz), 3.28 (1H, dd, J ) 14.2,
6.6 Hz), 3.56 (1H, dd, J ) 14.3, 5.6 Hz), 3.59 (3H, s), 4.28 (1H,
dddd, J ) 7.7, 7.7, 7.7, 2.8 Hz), 4.70 (1H, dddd, J ) 6.2, 6.2,
6.2, 5.9 Hz), 7.59 (2H, dd, J ) 8.4, 8.4 Hz), 7.68 (1H, dd, J )
7.7, 7.7 Hz), 7.92 (2H, d, J ) 7.9 Hz); 13C NMR (125.7 MHz) δ
12.0 (q), 16.0 (q), 18.7 (q), 21.8 (t), 22.6 (q), 22.8 (q), 23.8 (t),
24.2 (t), 27.8 (t), 27.9 (d), 28.1 (t), 31.3 (t), 35.3 (d), 35.78 (d),
35.82 (d), 36.2 (t), 38.3 (t), 39.0 (s), 39.5 (t), 39.9 (t), 40.2 (t),
42.3 (s), 47.7 (t), 48.1 (d), 51.6 (q), 56.3 (d), 56.6 (d), 60.6 (t),
74.4 (d), 77.7 (d), 128.1 (d × 2), 129.4 (d × 2), 134.0 (d), 139.5
(s), 174.1 (s); MS m/z (rel intensity) 558 (M+, 15), 77 (100).
11.4, 4.2 Hz), 2.84 (1H, dd, J ) 12.8, 8.3 Hz), 3.30 (1H, dd, J
) 14.3, 7.3 Hz), 3.57 (1H, dd, J ) 14.2, 5.3 Hz), 3.64 (3H, s),
4.62 (1H, dddd, J ) 8.5, 7.2, 5.8, 4.5 Hz), 7.59 (2H, dd, J )
7.8, 7.7 Hz), 7.68 (1H, dd, J ) 7.2, 7.1 Hz), 7.94 (2H, d, J )
8.4 Hz); 13C NMR (50.3 MHz) δ 12.0 (q), 18.6 (q), 19.3 (q), 22.6
(q), 22.8 (q), 23.8 (t), 24.1 (t), 25.3 (t), 26.3 (t), 27.8 (t), 27.9 (t),
28.0 (d), 35.75 (d), 35.79 (d), 36.0 (t), 39.5 (t), 39.8 (t), 42.5 (s),
46.1 (d), 51.4 (q), 51.9 (t), 52.3 (d), 56.3 (d), 59.6 (t), 74.3 (d),
89.8 (s), 128.0 (d × 2), 129.4 (d × 2), 134.0 (d), 139.4 (s), 175.1
(s); MS m/z (rel intensity) 576 (M+, 1), 77 (100). Anal. Calcd
for C33H52O6S: C, 68.71; H, 9.09; S, 5.56. Found: C, 68.87;
H, 9.26; S; 5.24.
Ack n ow led gm en t. This work was supported by the
Investigation Programme No. PB96-1461 of the Direc-
cio´n General de Investigacio´n Cient´ıfica y Te´cnica.
S.M.V. thanks the Ministerio de Educacio´n y Cultura,
Spain, for a fellowship.
Anal. Calcd for
C37H58O6S: C, 70.44; H, 9.27; S, 5.08.
Found: C, 70.56; H, 9.17; S, 5.28.
Rea ction of P er oxyh em ia ceta l 24 w ith (Dia cetoxy-
iod o)ben zen e-Iod in e. A solution of 24 (20 mg, 0.037 mmol)
in CH2Cl2 (2 mL) was treated with DIB (17 mg, 0.053 mmol)
and I2 (7 mg, 0.028 mmol) and irradiated as described above
for 30 min at 24-25 °C. Workup and methylation afforded a
residue that was purified by chromatotron chromatography
(hexanes-EtOAc 7:3), giving methyl (1′R,1′′′R,3′aS,3′′R,4′S,-
5′S,5′′S,7′aR)-3-[5′-[5′′-[(phenylsulfonyl)methyl]-3′′-methyl-
[1′′,2′′]dioxolan-3′′-yl]-1′-(1′′′,5′′′-dimethylhexyl)-7′a-methyloc-
tahydroinden-4′-yl]propanoate (37) (5 mg, 24%): amorphous;
IR 1729, 1309, 1152 cm-1; 1H NMR (500 MHz) δ 0.68 (3H, s),
0.87 (3H, d, J ) 6.5 Hz), 0.88 (3H, d, J ) 6.6 Hz), 0.91 (3H, d,
J ) 6.5 Hz), 1.27 (3H, s), 2.11 (1H, ddd, J ) 16.4, 12.3, 4.5
Hz), 2.25 (1H, dd, J ) 12.7, 4.5 Hz), 2.42 (1H, ddd, J ) 15.7,
Su p p or tin g In for m a tion Ava ila ble: Experimental pro-
cedures, physical properties, and spectroscopic data for com-
pounds 1-7 and 25-29; characterization of compounds 8, 9,
14, 18-22; X-ray data for compounds 25 and 33, including
tables of atomic coordinates, bond lengths, and bond angles
(23 pages). This material is contained in libraries on micro-
fiche, immediately follows this article in the microfilm version
of the journal, and can be ordered from the ACS; see any
current masthead page for ordering information.
J O980319Q