Regioselective oxyfunctionalization of unactivated carbons in steroids by a model of cytochrome P-450: Osmiumporphyrin complex/tert-butyl hydroperoxide system

Article abstract of DOI:10.1021/jo061800g

(Chemical Equation Presented) tert-Butyl hydroperoxide catalyzed by (5,10,15,20-tetramesitylporphyrinate) osmium(II) carbonyl [Os(TMP)CO] complex was found to be a highly efficient versatile oxidant for C-H carbons in steroid substrates. When reacted with representative steroids with an estrane, pregnane, 5β-cholane, or 5α-cholestane structure, regioselective oxyfunctionalization and/or oxidative degradation occurred to give a variety of novel and uncommon derivatives in one step.

Full text of DOI:10.1021/jo061800g

Regioselective Oxyfunctionalization of Unactivated Carbons in
Steroids by a Model of Cytochrome P-450: Osmiumporphyrin
Complex/tert-Butyl Hydroperoxide System
Takashi Iida,*,† Shoujiro Ogawa,† Keiji Hosoi,† Mitsuko Makino,‡ Yasuo Fujimoto,‡
Takaaki Goto,§ Nariyasu Mano,§ Junichi Goto,§,| and Alan F. Hofmann
Departments of Chemistry and General Studies, College of Humanities and Sciences, Nihon UniVersity,
Sakurajousui, Setagaya, Tokyo 156-8550, Japan, Graduate School of Pharmaceutical Sciences, Tohoku
UniVersity, Aobayama, Aoba-ku, Sendai 980-8578, Japan, Department of Pharmaceutical Sciences, Tohoku
UniVersity Hospital, 1-1 Seiryo-machi, Aoba-ku, Sendai 980-8574, Japan, and Department of Medicine,
UniVersity of California, San Diego, La Jolla, California 92093-0813
takaiida@chs.nihon-u.ac.jp
ReceiVed August 31, 2006
tert-Butyl hydroperoxide catalyzed by (5,10,15,20-tetramesitylporphyrinate) osmium(II) carbonyl [Os-
(TMP)CO] complex was found to be a highly efficient versatile oxidant for C-H carbons in steroid
substrates. When reacted with representative steroids with an estrane, pregnane, 5â-cholane, or
5R-cholestane structure, regioselective oxyfunctionalization and/or oxidative degradation occurred to give
a variety of novel and uncommon derivatives in one step.
Introduction
Recently, Higuchi et al.4 and other groups5,6 have reported a
powerful oxidant system consisting of 2,6-dichloropyridine
N-oxide (DCP N-oxide) as a single oxygen atom source, (meso-
5,10,15,20-tetramesitylporphyrinate) ruthenium(II) carbonyl [Ru-
(TMP)CO] complex (or its analogues) as a precatalyst, and HBr
as a cocatalyst. The system promotes highly efficient, stereo-
Oxyfunctionalizations of unactivated C-H bonds in hydro-
carbons are efficiently performed in ViVo by cytochrome P-450
enzymes, which carry a heme prosthetic group in the active
site.1 Such oxidations are of great interest from a mechanistic
standpoint and are also important biologically as they are often
the initial step in many detoxification pathways. Therefore, a
number of metalloporphyrin/oxygen transfer reagent systems
mimicking the P-450 enzymes have been developed for the
oxygenation of alkane, alkene, arene, and aromatic hydrocar-
bons.2,3
(2) Meunier, B. Chem. ReV. 1992, 92, 1411.
(3) Reese, P. B. Steroids 2001, 66, 481.
(4) (a) Ohtake, H.; Higuchi, T.; Hirobe, M. J. Am. Chem. Soc. 1992,
114, 10660. (b) Ohtake, H.; Higuchi, T.; Hirobe, M. Heterocycles 1995,
40, 867. (c) Higuchi, T.; Satake, C.; Hirobe, M. J. Am. Chem. Soc. 1995,
117, 8879. (d) Shingaki, T.; Miura, K.; Higuchi, T.; Hirobe, M.; Nagano,
T. Chem. Commun. 1997, 861.
(5) (a) Iida, T.; Ogawa, S.; Shiraishi, K.; Kakiyama, G.; Goto, T.; Mano,
N.; Goto, J. ARKIVOC 2003, Viii, 171. (b) Iida, T.; Ogawa, S.; Miyata, S.;
Goto, T.; Mano, N.; Goto, J.; Nambara, T. Lipids 2004, 39, 873. (c) Ogawa,
S.; Iida, T.; Goto, T.; Mano, N.; Goto, J.; Nambara, T. Org. Biomol. Chem.
2004, 2, 1013.
* Corresponding author. Telephone: 81-3-3329-1151. Fax: 81-3-3303-9899.
† Department of Chemistry, Nihon University.
‡ Department of General Studies, Nihon University.
§ Tohoku University.
| Tohoku University Hospital.
University of California, San Diego.
(1) Sono, M.; Roach, M. P.; Coulter, E. D.; Dawson, J. H. Chem. ReV.
1996, 96, 2841.
(6) Zhang, R.; Yu, W.-Y.; Che, C-H. Tetrahedron: Asymmetry 2005,
16, 3520.
10.1021/jo061800g CCC: $37.00 © 2007 American Chemical Society
Published on Web 01/10/2007
J. Org. Chem. 2007, 72, 823-830
823

Iida et al.
FIGURE 1. Os(TMP)CO/TBHP oxidant system.
TABLE 1. Effects of a Combination of Metalloporphyrin-Catalyzed Oxyfunctionalizations on the Reactivity and Regioselectivity of Substrate
3a
products, yield (%)b
oxygen
donor
reaction
time (h)
5â-hydroxy-
5â-hydroxy-
runa
precatalyst
solvent
temp
rt
rt
rt
50 °C
50 °C
80 °C
80 °C
80 °C
80 °C
3b
3c
3d
6-oxo
6R-hydroxy
15-oxo
24,20-lactone
1
2
3
4
5
6
7
8
9
Fe(TPFP)Cl
Mn(TPFP)Cl
Os(TMP)CO
Ru(TMP)CO
Os(TMP)CO
Os(TMP)CO
Os(TPP)CO
Os(TMP)CO
Os(TPFP)CO
PhIO
PhIO
PhIO
CH2Cl2
CH2Cl2
CH2Cl2
benzene
benzene
benzene
benzene
benzene
benzene
96
96
96
48
96
96
96
96
96
8
5
7
8
6
3
2
DCP N-oxide/HBr
DCP N-oxide/HBr
70% TBHP
TBHP
TBHP
TBHP
48
11
11
10
25
32
30
3
7
9
5
2
8
9
9
a For runs 1-3, the reaction mixtures contained substrate (5 mg, 11.4 µmol), PhIO (20 equiv), and precatalyst (0.008 equiv). For runs 4 and 5, the reaction
mixtures contained substrate (5 mg, 11.4 µmol), DCP N-oxide (3 equiv), precatalyst (0.004 equiv), 48% HBr (0.5 µl), and 4 Å molecular sieves (10 mg).
For runs 6-9, the reaction mixtures contained substrate (5 mg, 11.4 µmol), oxidant (20 equiv), precatalyst (0.004 equiv), and 4 Å molecular sieves (5 mg).
b Determined by capillary GC.
selective oxidation of olefins, alcohols, allylic alcohols, sulfides,
aromatic hydrocarbons, and alkanes with an excellent turnover
of the catalyst.
of the metalloporphyrin, Fe,7 Mn,7e,8 Ru,4-6,9 and Os10 were
compared, with aryl groups being the meso-substituents. On the
basis of previous findings,7-10 we examined the following
precatalysts: (5,10,15,20-tetrapentafluorophenylporphyrinate)
iron(III) chloride [Fe(TPFP)Cl]; (5,10,15,20-tetrapentafluo-
rophenylporphyrinate) manganese(III) chloride [Mn(TPFP)Cl];
Ru(TMP)CO; (5,10,15,20-tetraphenylporphyrinate) osmium(II)
carbonyl [Os(TPP)CO]; Os(TMP)CO; and (5,10,15,20-tetra-
pentafluorophenylporphyrinate) osmium(II) carbonyl [Os(TPF-
P)CO]. We found that varying the electron-donating and
electron-withdrawing substituents on the aromatic rings attached
at the meso-position on the porphyrin nucleus had little effect
As part of our effort to develop an effective metalloporphyrin
together with an oxygen donor for the oxyfunctionalization of
inactive C-H bonds in steroid substrates, we have developed
and report here a new powerful, unique oxidant, which involves
the combination of (meso-5,10,15,20-tetramesitylporphyrinate)
osmium(II) carbonyl [Os(TMP)CO] and tert-butyl hydroper-
oxide (TBHP) without a cocatalyst (Figure 1). Thus, the structure
on the left in Figure 1 should have two axial oxygen ligands
attached to the osmium atom; therefore, its oxidized analogue
(right) would possess one “O” and one “O2” axial ligand. The
way it is drawn now suggests that the dioxo complex is the
active oxidant. The system had regioselectivity differing from
that of the Ru(TMP)CO/DCP N-oxide/HBr system.4,5 We
describe the use of this system on compounds of the estrane
(1a), pregnane (2a), 5â-cholane (3a and 4a), and 5R-cholestane
(5a) series of steroids to yield a variety of novel and scarce
derivatives in one step. We also discuss factors governing the
O-insertion position, oxidative degradation, and regioselectivity
of the oxidant system.
(7) (a) Paulson, D. R.; Ullman, R.; Sloane, R. B.; Closs, G. L. J. Chem.
Soc., Chem. Commun. 1974, 186. (b) Mansuy, D.; Bartoli, J.-F.; Chottard,
J.-C.; Lange, M. Angew. Chem., Int. Ed. Engl. 1980, 19, 909. (c) Chauhan,
S. M. S.; Kandadai, A. S.; Jain, N.; Kumar, A. Chem. Pharm. Bull. 2003,
51, 1345. (d) Constantino, L.; Iley, J. Org. Biomol. Chem. 2004, 2, 1894.
(e) Rebelo, S. L. H.; Pereira, M. M.; Simo˜es, M. M. Q.; Neves, M. G. P.
M. S.; Cavaleiro, J. A. S. J. Catal. 2005, 234, 76.
(8) (a) Battioni, P.; Renaud, J. P.; Bartoni, J. F.; Reina-Artiles, M.; Fort,
M.; Mansuy, D. J. Am. Chem. Soc. 1988, 110, 8462. (b) Collman, J. P.;
Tanaka, H.; Hembre, R. T.; Brauman, J. I. J. Am. Chem. Soc. 1990, 112,
3689. (c) Banfi, S.; Maiocchi, A.; Moggi, A.; Montanari, F.; Quici, S. J.
Chem. Soc., Chem. Commun. 1990, 1794. (d) Breslow, R.; Huang, Y.;
Zhang, X.; Yang, J. Proc. Natl. Acad. Sci. U.S.A. 1997, 94, 11156. (e) Gross,
Z.; Simkhovich, L.; Galili, N. Chem. Commun. 1999, 599. (f) Yang, J.;
Weinberg, R.; Breslow, R. Chem. Commun. 2000, 531. (g) Belvedere, S.;
Breslow, R. Bioorg. Chem. 2001, 29, 321. (h) Collman, J. P.; Zeng, L.;
Decre´au, R. A. Chem. Commun. 2003, 2974. (i) Smith, J. R. L.; Iamamoto,
Y.; Vinhalo, F. S. J. Mol. Catal. A: Chem. 2006, 252, 23.
Results and Discussion
Table 1 shows the effects of a combination of metallopor-
phyrins/oxygen donors on the reactivity and regioselectivity of
the oxygenation of methyl 3R-acetoxy-5â-cholanoate (3a) as a
substrate. Our preliminary work was directed toward identifica-
tion of the optimal metalloporphyrin complex as a precatalyst
as well as the preferred oxygen-donating reagent. For the metal
(9) Groves, J. T.; Quinn, R. J. Am. Chem. Soc. 1985, 107, 5790.
(10) (a) Che, C.-M.; Chung, W.-C. J. Chem. Soc., Chem. Commun. 1986,
386. (b) Gross, Z.; Mahammed, A. J. Mol. Catal. A: Chem. 1999, 142,
367. (c) Li, Y.; Huang, J.-S.; Zhou, Z.-Y.; Che, C.-M. J. Am. Chem. Soc.
2001, 123, 4843.
824 J. Org. Chem., Vol. 72, No. 3, 2007

Oxyfunctionalization of UnactiVated Carbons
SCHEME 1
on the reactivity and selectivity. On the contrary, changing the
central metal ligand influenced strongly the efficiency of total
yields of each oxidized product.
Therefore, all of the oxidation reactions were carried out under
anhydrous conditions.
The Fe(TPFP)Cl/PhIO, Mn(TPFP)Cl/PhIO, and Os(TMP)-
CO/PhIO systems were unstable or inactive in oxyfunctional-
ization of the substrate 3a (runs 1-3). Although the oxidation
of 3a with the Ru(TMP)CO/DCP N-oxide/HBr system (run 4)
gave the 5â-hydroxy, 5â-hydroxy-15-oxo, and 5â-hydroxy-24,-
20-lactone derivatives in good yield,5 the analogous Os(TMP)-
CO/DCP N-oxide/HBr system (run 5) was inactive. All of the
TBHP oxidations catalyzed by (meso-tetraarylporphyrinate)
osmium(II) carbonyl [Os(TAP)CO] complexes (runs 7-9) in
the absence of water showed high reactivity and essentially
identical regioselectivity. In addition, the Os(TMP)CO/TBHP
system had a regioselectivity different from the Ru(TMP)CO/
DCP N-oxide/HBr one (run 4 versus 7). Thus, both the reactivity
and regioselectivity depend markedly upon a combination of
the central metal of the metalloporphyrins and the oxygen donor
counterparts. Of various combinations examined, the Os(TMP)-
CO/TBHP system was the most active. Its high oxidizing ability
seems to be closely related to the chemical nature of the Os
atom (e.g., OsO4).
The choice of oxygen-donating reagents such as iodosoben-
zene (PhIO),8d-i,10a,b DCP N-oxide,4-6 and TBHP7b,d was also
important, depending upon the accompanying precatalyst. The
combined use of PhIO or DCP N-oxide and Os(TMP)CO was
found to be less effective (see below). According to the previous
findings, DCP N-oxide is a specific oxygen donor against Ru-
(TMP)CO precatalyst,11 while PhIO itself is easily converted
into less active iodoxybenzene (PhIO2).12 In addition, the
presence of water in the reaction system would also accelerate
decomposition of an active trans-dioxoosmiumporphyrin inter-
mediate (see below).13 In this study, commercially available 70%
TBHP,7b,d instead of 30% H2O2,7c,8a,c was employed as a
peroxide because of its high active oxygen content as well as
easy handling. A comparative study (runs 6 versus 8 in Table
1) revealed that the use of anhydrous TBHP, which is easily
obtainable by organic solvent extraction (e.g., CH2Cl2) prior to
use, increased the yield about three times compared to that
obtained using 70% TBHP under the same reaction conditions.
Substrates examined in this study were five typical steroids
(1a-5a) belonging to the estrane, pregnane, 5â-cholane, and
5R-cholestane series. These compounds differed in the structures
of the A/B-ring and/or the side chains at C-17. To prevent the
simultaneous oxidation of hydroxyl groups in the substrates 1a,
(11) Higuchi, T.; Ohtake, H.; Hirobe, M. Tetrahedron Lett. 1989, 30,
6545.
(12) Nappa, M. J.; Tolman, C. A. Inorg. Chem. 1985, 24, 4711.
(13) Kuroda, Y.; Hiroshige, T.; Ogoshi, H. J. Chem. Soc., Chem.
Commun. 1990, 1594.
J. Org. Chem, Vol. 72, No. 3, 2007 825

Iida et al.
2a, 3a, and 5a to carbonyls, these compounds were protected
as their acetyl derivatives. All of the substrates were found to
react readily with the Os(TMP)CO/TBHP system to form a
variety of oxygenated compounds in one step. As shown in
Scheme 1, oxidation of estrone 3-acetate (1a) with Os(TMP)-
CO (0.004 equiv) and TBHP (20 equiv) in refluxing benzene
for 12 h resulted in regioselective ketonization at C-6 and
hydroxylation at C-9 to give the corresponding 6-oxo (1b, 12%
yield) and 9R-hydroxy-6-oxo (1c, 57%) derivatives, respectively,
with a total of 69% conversion. The predominant benzylic
oxygenation of 1a is similar to the results reported for the
oxidation of analogous estrane derivatives with Ru(TMP)CO/
DCP N-oxide/HBr,5b dimethyldioxirane,14 or TBHP/cobalt
acetate.15 When 3â-acetoxy-5R-pregnan-20-one (2a) was sub-
jected to the Os(TMP)CO/TBHP oxidation for 96 h, 3â-acetoxy-
5R-hydroxypregnan-20-one (2b, 29%) and 3â-acetoxy-5R-
androstan-17-one (2d, 35%) were isolated as the main products,
accompanied by a small amount of 3â-acetoxy-14R-hydroxy-
5R-pregnan-20-one (2c, 3%). Both the 5R- and 14R-hydroxyl-
ations proceeded with the complete retention of the configuration
at C-5 and C-14, as determined by the C-5 signal in 2b
appearing at 74.9 ppm16 and the C-14 signal in 2c occurring at
84.8 ppm17 in the 13C NMR spectra. These results suggest that
the electron-enriched C-5 and C-14 tertiary methine carbons
are more reactive than secondary methylene carbons, the latter
having electronic constraints. As a result, an oxygen atom is
preferentially inserted on the methine protons. A similar
electrophilic hydroxylation has also been reported for other
oxygen atom transfer reagents.5c,18,19 Furthermore, the insertion
of a 5â-hydroxyl group into less sterically hindered 5â-steroids
with cis A/B-ring fusion is generally accepted,18-21 whereas 5R-
hydroxylation is uncommon for more sterically crowded trans
5R-steroids. Therefore, the predominant formation in 2b is
particularly noteworthy, in analogy with the result reported for
the photooxygenation of 5R-androstane-3â,17â-diol diacetate
with peracetic acid22 or the reaction of palladium(II), thallium-
(III), and lead(IV) trifluoroacetates with 3â-acetoxyandrost-5-
en-7-one.23 Of additional interest was the formation of an
appreciable amount of 2d by the oxidative degradation of the
pregnane side chain in 2a.
FIGURE 2. Oxidative degradation mechanism of ketosteroids by
Baeyer-Villiger reaction.
and then oxidized as shown in Figure 2. The MS and 1H NMR
spectral data for 2d agreed completely with those of an authentic
specimen. The facile transformation, therefore, allows a new
entry to the synthesis of androstane-type compounds from the
20-ketopregnane derivatives.
We have previously reported5a that the oxidation of methyl
3R-acetoxy-5â-cholanoate (3a) with dimethyldioxirane or Ru-
(TMP)CO/DCP N-oxide/HBr affords methyl 3R-acetoxy-5â-
hydroxycholanoate (3b) and its dioxyfunctionalized analogues,
because of the favored steric and electron-enriched environments
at C-5 as mentioned above. However, when 3a was subjected
to the Os(TMP)CO/TBHP oxidation, methyl 3R-acetoxy-5R-
hydroxycholan-24-oate (3c, 9%) and methyl 3R-acetoxy-5R-
hydroperoxycholan-24-oate (3d, 9%) were obtained unexpect-
edly in moderate yield, along with the expected 3b (32%). The
similarity of cis 5â- and trans 5R-steroids (3a and 2a,
respectively) toward 5-hydroxylation (3b, 32% and 2b, 29%)
would suggest that steric effects of the substrates on the Os-
(TMP)CO/TBHP oxidation are less than those for Ru(TMP)-
CO/DCP N-oxide/HBr or dimethyldioxirane.4d,5a Although the
reason for the inversion of the A/B-ring fusion in the 5R-
oxygenated products (3c and 3d) is unclear, a similar 5R-
oxyfunctionalization with the oxidant was also observed for
other 5â-bile acids (unpublished results). To confirm the
presence of the hydroperoxy group, reduction of the hydrop-
eroxide 3d with triphenylphosphine25 gave rise to the deoxy-
genation product, the chromatographic data of which were
consistent with those for 3c. Further confirmatory evidence for
the structures of 3c and 3d was supported by measuring the
Numerous methods have been reported for the degradation
of the C21 20-ketopregnane type of steroids to the C19 17-
ketoandrostane derivatives.24 In the present case, 2d is probably
formed by the Baeyer-Villiger reaction at the 20-oxo group in
2a to give an ester intermediate, which in turn is hydrolyzed
1
1
several H-1H and H-13C shift-correlated 2D NMR spectra.
Table 2 shows the complete H and 13C resonance assign-
1
ments of 3c and 3d. In the 13C NMR spectra, the R-carbon atoms
having acetoxy and hydroxyl groups resonated at 71.0 and 73.2
ppm in 3c and at 70.0 and 83.6 ppm in 3d, indicating that one
hydroxyl function was inserted into 3a. The C-3 signal appearing
at 74.3 ppm in 3a was shifted upfield by 3.3 ppm and resonated
at 71.0 ppm in 3c and at 70.0 ppm in 3d in the 1H-13C
HETCOR spectra, probably owing to the γ-effect of the
R-carbon at C-5. On the other hand, the 3â-H signal at 4.72
ppm as a multiplet in 3a was deshielded by 0.47 ppm in 3c
(0.32 ppm in 3d) and occurred at 5.19 ppm (5.04 ppm).
Although the 13C chemical shifts of the C-1 to C-7 in 3c and
3d agreed very well with those reported for 5R-cholestan-3R,5R-
diol 3-acetate,26 the remaining signals were almost unchanged
(14) Brown, D. S.; Marples, B. A.; Muxworthy, J. P.; Baggaley, K. H.
J. Chem. Res., Synop. 1992, 28.
(15) Modica, E.; Bombieri, G.; Colombo, D.; Marchini, N.; Ronchetti,
F.; Scala, A.; Toma, L. Eur. J. Org. Chem. 2003, 2964.
(16) (a) Blunt, J. W. Aust. J. Chem. 1975, 28, 1017. (b) Eggert, H.;
VanAntwerp, C. L.; Bhacca, N. S.; Djerassi, C. J. Org. Chem. 1976, 41,
71.
(17) Iida, T.; Shiraishi, K.; Ogawa, S.; Goto, T.; Mano, N.; Goto, J.;
Nambara, T. Lipids 2003, 38, 281.
(18) Cerre`, C.; Hofmann, A. F.; Schteingart, C. D.; Jia, W.; Maltby, D.
Tetrahedron 1997, 53, 435.
(19) Iida, T.; Yamaguchi, T.; Nakamori, R.; Hikosaka, M.; Mano, N.;
Goto, J.; Nambara, T. J. Chem. Soc., Perkin Trans. 1 2001, 2229.
(20) Arnone, A.; Cavicchioli, M.; Montanari, V.; Resnati, G. J. Org.
Chem. 1994, 59, 5511.
(21) Be´gue´, J.-P. J. Org. Chem. 1982, 47, 4268.
(22) Rotmann, A.; Mazur, Y. J. Am. Chem. Soc. 1972, 94, 6228.
(23) Ruddock, P. L.; Williams, D. J.; Reese, P. B. Steroids 2004, 69,
193.
(24) Oliveto, E. P. In Organic Reactions in Steroid Chemistry: Synthesis
and Degradation of the Pregnane Side-Chain; Fried, J., Edwards, J. A.,
Eds.; Van Nostrand Reinhold: New York, 1971; Vol. II, pp 127-236.
(25) Fukuyama, Y.; Kubo, M.; Minami, H.; Yuasa, H.; Matsuo, A.; Fujii,
T.; Morisaki, M.; Harada, K. Chem. Pharm. Bull. 2005, 53, 72-80.
(26) VanAntwerp, C. L.; Eggert, H.; Meakins, G. D.; Miners, J. O.;
Djerassi, C. J. Org. Chem. 1977, 42, 789.
826 J. Org. Chem., Vol. 72, No. 3, 2007

Oxyfunctionalization of UnactiVated Carbons
1
TABLE 2. Complete H and 13C Chemical Shifts of 5r-Oxygenated Compounds 3c and 3da
3c
1H
3d
1H
3a
carbon No. type
13C
type
13C
type 13Cb
1Hc
R
â
1.39
1.78
5.19 (m) CH
1.86
R
â
1.21
1.74
5.04 (m) CH
1.65
R
â
1
2
3
4
5
6
7
8
9
CH2
CH2
CH
CH2
C
CH2
CH2
CH
CH
C
25.6 1.77
25.6 1.39
71.0
CH2
CH2
26.6 1.73
25.5 1.32
70.0
CH2
CH2
35.0 1.75
26.3 1.29
74.3
0.94
1.60
3.51
1.45
1.35
1.83
1.39
1.38
37.4 1.61
73.2
33.6 1.31
26.8 1.56
34.9
CH2
C
31.6 2.08
83.6
28.0 1.31
25.3 1.39
35.0
CH2
CH
CH2
CH2
CH
CH
C
32.2 1.71
41.9
27.0 1.23
26.6 1.09
35.7
1.49
1.33
1.37
CH2
CH2
CH
CH
C
1.73
1.85
1.38
45.2 1.56
39.5
45.0 1.43
39.4
40.4 1.41
34.5
10
11 CH2
12 CH2
20.9 1.35
40.0 1.16
42.7
1.19
1.94
CH2
CH2
C
20.9 1.32
39.9 1.10
42.7
1.18
1.91
CH2
CH2
C
20.8 1.38
40.1 1.14
42.7
1.23
1.96
13
C
14 CH
15 CH2
16 CH2
17 CH
18 CH3
19 CH3
20 CH
21 CH3
22 CH2
23 CH2
56.1 1.14
24.0 1.01
28.1 1.85
55.8 1.10
12.1 0.64 (s)
15.9 0.93 (s)
35.4 1.38
18.2 0.89 (d, 6.5)
31.0 1.30, 1.77 (each, m)
31.1 2.20, 2.33 (each, m)
174.8
CH
CH2
CH2
CH
CH3
CH3
CH
CH3
CH2
CH2
C
56.1 1.05
24.0 1.01
28.1 1.84
55.8 1.09
12.1 0.63 (s)
16.1 0.98 (s)
35.4 1.39
18.2 0.88 (d, 6.5)
31.0 l.30, 1.75 (each, m)
31.1 2.06, 2.33 (each, m)
174.8
CH
CH2
CH2
CH
CH3
CH3
CH
CH3
CH2
CH2
C
56.4 1.05
24.1 1.04
28.1 1.85
56.0 1.10
12.0 0.64 (s)
23.3 0.91 (s)
35.3 1.41
18.2 0.92 (d)
31.0 1.29, 1.75 (each, m)
31.0 2.12, 2.32 (each, m)
174.3
51.4
1.56
1.24
1.57
1.24
1.56
1.27
24
COOCH3 CH3
OCOCH3
OCOCH3 CH3
C
51.5 3.66
169.3
21.5 2.04
CH3
C
CH3
51.5 3.66
170.1
21.7 2.09
CH3
C
CH3
C
170.6
21.4
a Measured in CDCl3. Chemical shifts were expressed as δ ppm relative to Me4Si. Abbreviations used: s, singlet; d, doublet; m, multiplet. Values in
parentheses refer to signal multiplicity and coupling constant (J in Hz). b Measured in CDCl3 at 270 MHz. c As the C-3 free alcohol (ref 34).
from 3a. These findings indicate that the C-8 and C-9 tertiary
methine carbons are excluded from hydroxylation, whereas
hydroxylation occurs readily at the C-5 methine carbon situated
in the vicinity of the 3R-acetoxyl group. The supporting evidence
for 3c and 3d was the presence of a correlation peak between
the 19-methyl protons and the C-5 quaternary carbon in the
heteronuclear multiple bond connectivity (HMBC) spectra owing
reagent to yield a single component, which agreed completely
with 4d, according to their chromatographic and spectral
comparisons.
The oxygenation of 5R-cholestan-3â-yl acetate (5a) with Os-
(TMP)CO/TBHP resulted in the formation of 3â-acetoxy-
cholestan-5R-ol (5b, 16%) and 3â-acetoxy-5R-cholestan-25-ol
(5c, 33%) in an approximate ratio of 1:2. Again, a direct 5R-
hydroxylation was attained for 5a to produce 5b. For 5c, the
easy attack on the electron-enriched C-25 isopropylic methine
carbon in 5a is common for oxygen transfer reagents5,18,19 and
supports the electrophilicity of the osmiumporphyrin complex.
Our previous study19 revealed that the oxidation product of 5a
with dimethyldioxirane is a mixture of four components
consisting of 5b and its dioxygenated derivatives at the C-14,
C-17, and C-20 positions. The oxyfunctionalization of 5a with
Os(TMP)CO/TBHP is, therefore, more regioselective than that
observed with dimethyldioxirane.
Although the mechanism for a single atom oxygen activation
and transfer, generated by the Os(TMP)CO/TBHP system, is not
yet certain, a possible pathway would proceed Via an active trans-
dioxoosmiumporphyrin intermediate from the precatalyst,8i,10b,28
as outlined by the insertion of an oxygen atom into a methine
carbon in Figure 3. The results suggest that the oxidized osmium
complex reacts with the substrates to generate a radical with a
lifetime long enough for inversion to occur (see products from
3a). Possibly a metalloporphyrin peroxy radical attacks the C-H
bond, generating an osmiumporphyrin hydroperoxide and alkyl
radical. Particularly noteworthy is a direct 5-hydroxylation on
both 5R- and 5â-steroids and the Baeyer-Villiger reaction of
ketosteroids as well as the oxyfunctionalization at methine and
benzylic carbons. Therefore, the Os(TMP)CO/TBHP system
1
to the long-range H-13C coupling. In contrast, in each of the
ROESY spectra the 19-methyl signal was correlated with the
2â-H and 4â-H owing to the 1,3-diaxial relationship, suggesting
the trans A/B-ring fusion in 3c and 3d. The molecular ion M+
in the low-resolution mass spectrometry (LRMS) and the ion-
adducted molecule [M + Na]+ in the high-resolution mass
spectrometry (HRMS) (see Experimental Section) also supported
each of the proposed structures of 3c and 3d.
A much different result was obtained when methyl 3-oxo-
5â-cholan-24-oate (4a), differing only in the C-3 function from
3a, was treated with Os(TMP)CO/TBHP. The isolated products
were identified as methyl 3,4-seco-5â-cholan-24-oate-3,4-dioic
acid (4d, 35%), accompanied by two minor components, methyl
3-oxo-5â-hydroxycholan-24-oate (4b, 8%) and methyl 3-oxo-
4-cholen-24-oate (4c, 10%). The conjugated enone 4c would
be derived by the subsequent elimination of the 5â-hydroxyl
group from 4b. As mentioned above, the oxidative cleavage of
4a by Baeyer-Villiger reaction24 would preferentially occur at
the C-3 position to give an intermediary lactone derivative,
which on hydrolysis and subsequent oxidation yields the 3,4-
seco dicarboxylic acid 4d (Figure 2). To confirm the structure
of 4d, methyl 3â,4â-dihydroxy-5â-cholanoate, prepared from
lithocholic acid in several steps,27 was oxidized with Jones
(27) Iida, T.; Momose, T.; Chang, F. C.; Goto, J.; Nambara, T. Chem.
Pharm. Bull. 1989, 37, 3323.
(28) Groves, J. T. Inorg. Biochem. 2006, 100, 434.
J. Org. Chem, Vol. 72, No. 3, 2007 827

Iida et al.
FIGURE 3. Possible mechanism of Os(TMP)CO-catalyzed hydroxylation of unactivated C-H saturated carbons by TBHP.
al.29 The Os(TAP)CO complexes were prepared from the tet-
raarylporphyrins and Os3(CO)12 by the method reported by Che et
al.30
promises to be a useful tool for selective, efficient synthesis of
bioactive, hydrophilic steroids from less active, lipophilic
resources, which are abundantly available in nature. Further
exploration of the scope of the Os(TMP)CO/TBHP system based
on oxyfunctionalization will be reported in due course.
General Procedure for the Oxyfunctionalization by Os(TMP)-
CO/TBHP. To a solution of steroid (1.4 mmol) and molecular
sieves (250 mg; 4 Å) in benzene (5 mL), Os(TMP)CO (6 mg, 5.5
µmol) and anhydrous TBHP (1.9 mL, 28 mmol) were successively
added, and the mixture was refluxed for 12-96 h. The reaction
was monitored by TLC. After the reaction, each of the products
was isolated by passage through an open column chromatography
on silica gel, followed by NP- (or RP-) MPLC or by preparative
RP-HPLC.
Oxyfunctionalization Products of Estrone 3-Acetate (1a).
3-Acetoxyestra-1,3,5(10)-triene-6,17-dione (1b). 1b was isolated
from the reaction product of 1a as colorless thin plates [fraction
(Fr. 1)] crystallized from EtOAc; mp 186-189 °C (lit.,5b mp 186-
189 °C); IR νmax/cm-1 1767, 1738, 1680 (CdO); 1H NMR (CDCl3)
δ: 0.92 (3H, s, 18-CH3), 2.32 (3H, s, -COCH3), 7.27 (1H, dd, J1
) 8.3, J2 ) 2.4 Hz, 2-H), 7.48 (1H, d, J ) 8.1 Hz, 1-H), 7.77 (1H,
d, J ) 2.4 Hz, 4-H); 13C NMR δ: 13.6 (C-18), 20.9 (OCOCH3),
21.3 (C-15), 25.0 (C-11), 31.1 (C-12), 35.6 (C-16), 39.1 (C-8), 43.0
(C-7 and C-9), 47.5 (C-13), 50.2 (C-14), 120.1 (C-4), 126.6 (C-2),
127.1 (C-1), 133.5 (C-5), 143.3 (C-10), 149.3 (C-3), 169.3
(OCOCH3), 196.3 (C-6), 219.5 (C-17); LR-EI-MS m/z 326 (M+,
18%), 284 (M - part of ring D, 100), 266 (M-AcOH, 5), 240
(12), 227 (14).
Experimental Section
Materials and Methods. Melting points (mp) were determined
on an electric micro hot stage and were uncorrected. Infrared (IR)
spectra were obtained on a spectrometer for samples in KBr tablets.
Proton (1H) and carbon (13C) were obtained on an NMR instrument
at 270 and 67.8 MHz, respectively, with CDCl3 containing 0.1%
Me4Si as the solvent; chemical shifts are expressed as δ (ppm)
relative to Me4Si. 13C NMR signals corresponding to the methyl
(CH3), methylene (CH2), methine (CH), and quaternary (C) carbons
were differentiated by means of DEPT experiment. LRMS spectra
were recorded by gas chromatography-mass spectrometry (GC-
MS) at 70 eV with an electron ionization (EI) probe using the
positive ion mode (PIM). HRMS spectra were performed using a
mass spectrometer equipped with an electrospray ionization (ESI)
probe using the PIM. A gas chromatograph equipped with a flame
ionization detector was used isothermally at 280 °C fitted with a
chemically bonded fused silica capillary column (25 m × 0.32 mm
i.d.; film thickness, 0.25 µm). Preparative high-performance liquid
chromatography (HPLC) apparatus consisted of a pump equipped
with a RI detector and an ODSPH column (250 mm × 10 mm
i.d.) using methanol/water (9:1-8:2, v/v) as eluent. The apparatus
used for normal-phase (NP) medium-pressure liquid chromatogra-
phy (MPLC) consisted of an RI detector and uf-3040 chromato-
graphic pump using silica gel 60 (230-400 mesh) as adsorbent
and hexane/EtOAc (9:1-8:2, v/v) mixtures as eluent. Reversed-
phase (RP) MPLC was carried out by using Cosmosil 75C18-PREP
as adsorbent and methanol/water (9:1-8:2, v/v) as eluent. Thin layer
chromatography (TLC) was performed on precoated silica gel 60F254
plates (0.25-mm layer thickness) using hexane/EtOAc (8:2-1:1,
v/v) mixtures as developing solvent. RP-TLC was carried out on
precoated RP-18F254S plates (Merck) using methanol/water (9:1-
8:2, v/v) as developing solvent.
3-Acetoxy-9r-hydroxyestra-1,3,5(10)-triene-6,17-dione (1c).
1c was isolated from the reaction product of 1a as colorless needles
(Fr. 2) crystallized from EtOAc; mp 216-219 °C (lit.,5b mp 216-
1
219 °C); IR νmax/cm-1 3519 (OH), 1760, 1745 (CdO); H NMR
(CDCl3) δ: 0.91 (3H, s, 18-CH3), 2.32 (3H, s, -COCH3), 7.22
(1H, dd, J1 ) 8.8, J2 ) 2.4 Hz, 2-H), 7.41 (1H, d, J ) 8.3 Hz,
1-H), 7.77 (1H, d, J ) 2.4 Hz, 4-H); 13C NMR δ: 12.7 (C-18),
20.9 (C-15), 21.1 (OCOCH3), 27.3 (C-11), 31.9 (C-12), 35.6 (C-
16), 36.6 (C-7), 40.8 (C-8), 43.4 (C-14), 47.4 (C-13), 69.3 (C-9),
120.8 (C-4), 125.6 (C-2), 127.3 (C-1), 134.0 (C-5), 144.4 (C-10),
150.7 (C-3), 169.3 (OCOCH3), 196.6 (C-6), 219.4 (C-17); LR-EI-
MS m/z 342 (M+, 35%), 324 (M - H2O, 1), 300 (M-part of ring
D, 100), 282 (M - H2O - part of ring D, 19), 243 (7), 215 (23).
Oxyfunctionalization Products of 3â-Acetoxy-5r-pregnane-
20-one (2a). 3â-Acetoxy-5r-androstan-17-one (2d). 2d was
isolated from the reaction product of 2a as a colorless amorphous
solid (Fr. 1) crystallized from petroleum ether; mp 103-104 °C
(lit.,31 mp 103-104 °C); IR νmax/cm-1 1737 (CdO); 1H NMR
(CDCl3) δ: 0.85 (3H, s, 18-CH3), 0.86 (3H, s, 19-CH3), 2.02 (3H,
s, -COCH3), 4.69 (1H, brm, 3R-H); 13C NMR δ: 12.2 (C-19),
13.8 (C-18), 20.4 (C-11), 21.4 (OCOCH3), 21.8 (C-15), 27.4 (C-
2), 28.2 (C-6), 30.8 (C-4), 31.5 (C-7), 33.9 (C-1), 35.0 (C-8), 35.6
(C-10), 35.8 (C-16), 36.7 (C-12), 44.6 (C-5), 47.8 (C-13), 51.3 (C-
9), 54.3 (C-14), 73.5 (C-3), 170.7 (OCOCH3), 221.2 (C-17); LR-
EI-MS m/z 332 (M+, 39%), 314 (M - H2O, 4), 288 (15), 272 (M
- AcOH, 100), 257 (M - AcOH - CH3, 39), 239 (M - AcOH -
2D NMR spectra were recorded at 23 °C for ca. 0.05 mM
solutions in CDCl3 in a 5-mm tube on an instrument (600 and 149.4
MHz for 1H and 13C, respectively). 1H and 13C signal assignments
were made using a combination of 2D homonuclear (1H-1H) and
heteronuclear (1H-13C) shift-correlated techniques, which included
1H-1H COSY, long-range 1H-1H COSY, 1H-1H rotational nuclear
Overhauser effect (ROESY), 1H-13C HETCOR, 1H detected
heteronuclear multiple quantum coherence (HMQC), and 1H
detected HMBC experiments. These 2D NMR spectra were
recorded by using standard pulse sequence and parameters recom-
mended by the manufacturer.
Estrone 3-acetate (1a) was purchased from a commercial supplier.
5R-Pregnan-3â-ol-20-one 3-acetate (2a) was prepared from 5-preg-
nen-3â-ol-20-one (pregnenolone) by the usual manner. The remain-
ing steroid substrates (3a-5a) were from our laboratory collection.
70% TBHP was purchased from a commercial supplier. It was
extracted with CH2Cl2, and the organic layer was evaporated under
reduced pressure prior to use. meso-Tetraarylporphyrins were
prepared by a slight modification of the procedure of Lindsey et
(29) Lindsey, J. S.; Schreiman, I. C.; Hsu, H. C.; Kearney, P. C.;
Margurettaz, A. M. J. Org. Chem. 1987, 52, 827.
(30) Che, C.-M.; Poon, C.-K.; Chung, W.-C.; Gray, H. B. Inorg. Chem.
1985, 24, 1277.
(31) Cardwell, H. M. E.; Cornforth, J. W.; Duff, S. R.; Holtermann, H.;
Robinson, R. J. Chem. Soc. 1953, 361.
828 J. Org. Chem., Vol. 72, No. 3, 2007

Oxyfunctionalization of UnactiVated Carbons
H2O - CH3, 13), 228 (15), 218 (M - AcOH - H2O - ring D,
59), 201 (42), 108 (51).
3â-Acetoxy-5r-hydroxypregnane-20-one (2b). 2b was isolated
from the reaction product of 2a as a colorless amorphous solid (Fr.
24-oate (4a). Methyl 3-Oxo-4-cholene-24-oate (4c). 4c was
isolated from the reaction product of 4a as a colorless amorphous
solid (Fr. 1) crystallized from aqueous acetone; mp 124-126 °C
(lit.,32 mp 126-127 °C); IR νmax/cm-1 1616, 3008 (CdO) 1736,
1677 (CdO); 1H NMR (CDCl3) δ: 0.71 (3H, s, 18-CH3), 0.91 (3H,
d, J ) 6.2 Hz, 21-CH3), 1.18 (3H, s, 19-CH3), 3.67 (3H, s,
-COOCH3), 5.73 (1H, s, 4-H); 13C NMR δ: 11.9 (C-18), 17.3
(C-19), 18.2 (C-21), 21.0 (C-11), 24.1 (C-15), 28.0 (C-16), 30.9,
31.0 (C-22, C-23), 32.0 (C-7), 32.9 (C-6), 33.9 (C-2), 35.3 (C-20),
35.6 (C-8), 35.7 (C-1), 38.6 (C-10), 39.6 (C-12), 42.4 (C-13), 51.1
(COOCH3), 53.7 (C-9), 55.7, 55.8 (C-14, C-17), 123.7 (C-4), 171.6
(C-5), 174.7 (C-24), 199.6 (C-3); LR-EI-MS m/z 386 (M+, 24),
371 (M - CH3, 5), 344 (M - CH2CO, 8), 329 (M - CH3 - CH2-
CO, 8), 313 (4), 271 (M - S.C., 14), 229 (M - S.C. - ring D,
100), 211 (M - H2O - S.C. - ring D, 21).
3) crystallized from aqueous methanol; mp 179-183 °C; IR νmax
/
1
cm-1 3422 (OH), 1729, 1685 (CdO); H NMR (CDCl3) δ: 0.60
(3H, s, 18-CH3), 1.00 (3H, s, 19-CH3), 2.02 (3H, s, -COCH3),
2.12 (3H, s, 21-CH3), 5.16 (1H, brm, 3R-H); 13C NMR δ: 13.5
(C-18), 16.0 (C-19), 21.2 (C-11), 21.4 (OCOCH3), 22.8 (C-16),
24.3 (C-15), 25.8 (C-2), 26.7 (C-7), 30.5 (C-1), 31.5 (C-21), 34.5
(C-6), 34.7 (C-8), 38.8 (C-10), 39.0 (C-4), 40.1 (C-12), 44.3 (C-
13), 45.4 (C-9), 56.3 (C-14), 63.7 (C-17), 70.7 (C-3), 74.9 (C-5),
170.7 (OCOCH3), 209.7 (C-20); LR-EI-MS m/z 376 (M+, 3%), 358
(M - H2O, 33), 340 (M - 2H2O, 2), 316 (M - AcOH, 14), 298
(M - AcOH - H2O, 100), 283 (M - AcOH - H2O - CH3, 38),
262 (91), 255 (M - AcOH - H2O - ring D, 25), 213 (39); HR-
EI-MS, calcd for C23H36O4 [M]+, 376.2614; found, m/z, 376.2600.
3â-Acetoxy-14r-hydroxy-5r-pregnane-20-one (2c). 2c was
isolated from the reaction product of 2a as colorless amorphous
solid (Fr. 2) crystallized from aqueous methanol; mp 164-168 °C;
Methyl 5â-Hydroxy-3-oxocholan-24-oate (4b). 4b was isolated
from the reaction product of 4a as a colorless amorphous solid (Fr.
2) crystallized from aqueous acetone; mp 170-172 °C (lit.,5a mp
1
170-172 °C); IR νmax/cm-1 3382 (OH), 1741, 1702 (CdO); H
NMR (CDCl3) δ: 0.68 (3H, s, 18-CH3), 0.91 (3H, d, J ) 6.5 Hz,
21-CH3), 1.00 (3H, s, 19-CH3), 3.67 (3H, s, -COOCH3); 13C NMR
δ: 12.0 (C-18), 16.1 (C-19), 18.2 (C-21), 21.6 (C-11), 24.0 (C-
15), 28.0 (C-16), 29.0 (C-7), 30.9 (C-22 and C-23), 31.1 (C-1),
34.7 (C-8), 35.2 (C-20), 36.1 (C-6), 37.3 (C-2), 39.7 (C-12), 40.1
(C-10), 42.5 (C-13), 43.6 (C-9), 49.3 (C-4), 51.4 (COOCH3), 55.7
(C-17), 56.4 (C-14), 78.4 (C-5), 174.6 (C-24), 211.6 (C-3); LR-
EI-MS m/z 386 (M - H2O, 23), 355 (M - 2H2O - CH3, 3), 329
(M - H2O - CH3 - CH2CO, 6), 229 (M - H2O - S.C. - ring
D, 100), 211 (M - 2H2O - S.C. - ring D, 24).
1
IR νmax/cm-1 3424 (OH), 1733, 1687 (CdO); H NMR (CDCl3)
δ: 0.82 (3H, s, 18-CH3), 0.97 (3H, s, 19-CH3), 2.02 (3H, s,
-COCH3), 2.23 (3H, s, 21-CH3), 4.68 (1H, brm, 3R-H); 13C NMR
δ: 12.1 (C-19), 15.3 (C-18), 20.8 (C-11), 21.4 (OCOCH3), 24.9
(C-16), 27.4 (C-7), 27.6 (C-2), 28.5 (C-6), 33.4 (C-12 and C-21),
33.8 (C-4), 35.7 (C-10), 36.9 (C-1), 39.0 (C-15), 39.8 (C-8), 44.3
(C-5), 49.2 (C-9 and C-13), 62.3 (C-17), 73.6 (C-3), 84.8 (C-14),
170.7 (OCOCH3), 217.9 (C-20); LR-EI-MS m/z 376 (M+, 19%),
358 (M - H2O, 30), 348 (88), 333 (M - S.C., 10), 315 (M - H2O
- S.C., 7), 290 (62), 283 (M - AcOH - H2O - CH3, 3), 272
(100), 255 (M - AcOH - H2O - ring D, 10); HR-EI-MS, calcd
for C23H36O4 [M]+, 376.2613; found, m/z, 376.2616.
Methyl 3,4-Seco-5â-cholan-24-oate-3,4-dioic Acid (4d). 4d was
isolated from the reaction product of 4a as colorless needles (Fr.
3) crystallized from acetone; mp 242-245 °C; IR νmax/cm-1 3449
1
Oxyfunctionalization Products of Methyl 3r-Acetoxy-5â-
cholan-24-oate (3a). Methyl 3r-Acetoxy-5r-hydroxycholan-24-
oate (3c). 3c was isolated from the reaction product of 3a as
colorless needles (Fr. 1) crystallized from EtOAc/hexane; mp 123-
127 °C; IR νmax/cm-1 3449 (OH), 1735 (CdO); LR-EI-MS m/z
448 (M+, 1%), 430 (M - H2O, 28), 415 (M - H2O - CH3, 3),
388 (M - AcOH, 5), 370 (M - AcOH - H2O, 100), 355 (M -
AcOH - H2O - CH3, 35), 334 (66), 273 (M - AcOH - S.C.,
12), 255 (M - AcOH - H2O - S.C., 20), 213 (M - AcOH -
H2O - S.C. - ring D, 46); HR-ESI-MS, calcd for C27H44O5Na
[M + Na]+, 471.3086; found, m/z, 471.3051.
(OH), 1739, 1703 (CdO); H NMR (CDCl3) δ: 0.66 (3H, s, 18-
CH3), 0.91 (3H, d, J ) 6.2 Hz, 21-CH3), 0.96 (3H, s, 19-CH3),
3.66 (3H, s, -COOCH3); 13C NMR δ: 12.1 (C-18), 18.2 (C-21),
19.0 (C-19), 21.5 (C-11), 24.1 (C-15), 24.6 (C-6), 26.3 (C-7), 28.1
(C-16), 28.8 (C-2), 31.0 (C-22 and C-23), 33.8 (C-1), 35.3 (C-8),
35.4 (C-20), 36.7 (C-10), 39.9 (C-12), 42.5 (C-13), 45.6 (C-9), 48.1
(C-5), 51.5 (COOCH3), 55.8 (C-14 and C-17), 174.8 (C-24), 180.7,
181.3 (C-3, C-4); LR-EI-MS m/z 436 (M+, 5%), 418 (M - H2O,
100), 400 (M - 2H2O, 9), 390 (53), 345 (45), 335 (35), 317 (42),
276 (54), 275 (M - 2H2O - S.C., 48), 221 (60).
Oxyfunctionalization Products of 5r-Cholestan-3â-yl-acetate
(5a). 3â-Acetoxycholestan-5r-ol (5b). 5b was isolated from the reac-
tion product of 5a as a colorless amorphous solid (Fr. 1) crystallized
from aqueous methanol; mp 180-182 °C (lit.,33 mp 185-186 °C);
Methyl 3r-Acetoxy-5r-hydroperoxycholan-24-oate (3d). 3d
was isolated from the reaction product of 3a as colorless needles
(Fr. 2) crystallized from EtOAc/hexane; mp 153-156 °C; IR νmax
/
cm-1 3449 (OH), 1736 (CdO); LR-EI-MS m/z 464 (M+, 1%), 446
(M - H2O, 7), 430 (M - H2O2, 30), 388 (35), 370 (M - AcOH
- H2O2, 100), 355 (M - AcOH - H2O - CH3, 24), 334 (75), 273
(M - AcOH - S.C., 19), 255 (M - AcOH - H2O2 - S.C., 27),
213 (M - AcOH - H2O2 - S.C. - ring D, 35); HR-ESI-MS,
calcd for C27H44O6Na [M + Na]+, 487.3036; found, m/z, 487.3078.
Methyl 3r-Acetoxy-5â-hydroxycholan-24-oate (3b). 3b was
isolated from the reaction product of 3a as colorless needles (Fr.
3) crystallized from benzene/hexane; mp 175-177 °C (lit.,19 mp
1
IR νmax/cm-1 3449 (OH), 1736, 1704 (CdO); H NMR (CDCl3)
δ: 0.65 (3H, s, 18-CH3), 0.86 (6H, d, J ) 6.5 Hz, 26- and 27-
CH3), 0.90 (3H, d, J ) 6.5 Hz, 21-CH3), 1.00 (3H, s, 19-CH3),
2.02 (3H, s, -COCH3), 5.16 (1H, brm, 3R-H); 13C NMR δ: 12.1
(C-18), 16.1 (C-19), 18.6 (C-21), 21.3 (C-11), 21.5 (OCOCH3),
22.6 (C-26), 22.8 (C-27), 23.9 (C-23), 24.1 (C-15), 25.9 (C-7), 26.8
(C-2), 28.0 (C-25), 28.2 (C-16), 30.5 (C-1), 34.5 (C-6), 34.7 (C-
8), 35.8 (C-20), 36.2 (C-22), 38.8 (C-10), 39.5 (C-24), 40.0 (C-4
and C-12), 42.7 (C-13), 45.6 (C-9), 56.1 (C-14), 56.2 (C-17), 70.9
(C-3), 75.0 (C-5), 170.7 (OCOCH3); LR-EI-MS m/z 446 (M+, 4%),
428 (M - H2O, 66), 413 (M - H2O - CH3, 4), 386 (M - AcOH,
9), 368 (M - AcOH - H2O, 100), 353 (M - AcOH - H2O -
CH3, 37), 332 (45), 274 (31), 228 (36), 213 (54).
1
175-177 °C); IR νmax/cm-1 3454 (OH), 1735, 1708 (CdO); H
NMR (CDCl3) δ: 0.64 (3H, s, 18-CH3), 0.90 (3H, s, 19-CH3), 0.91
(3H, d, J ) 7.3 Hz, 21-CH3), 2.02 (3H, s, -COCH3), 3.67 (3H, s,
-COOCH3), 5.08 (1H, brm, 3â-H); 13C NMR δ: 12.0 (C-18), 16.3
(C-19), 18.2 (C-21), 21.1 (C-11), 21.4 (OCOCH3), 24.2 (C-15),
26.1 (C-2), 28.1 (C-16), 28.6 (C-7), 29.4 (C-1), 31.0 (C-22 and
C-23), 34.9 (C-8), 35.3 (C-20), 36.9 (C-6), 38.1 (C-4), 39.6 (C-
10), 39.8 (C-12), 42.5 (C-13), 43.2 (C-9), 51.5 (COOCH3), 55.8
(C-17), 56.5 (C-14), 71.4 (C-3), 75.4 (C-5), 170.5 (OCOCH3), 174.7
(C-24); LR-EI-MS m/z 430 (M - H2O, 8), 370 (M - AcOH -
H2O, 16), 334 (38), 273 (M - AcOH - S.C., 23), 255 (M - AcOH
- H2O - S.C., 56), 228 (M - AcOH - H2O - S.C. - part of
ring D, 33), 213 (M - AcOH - H2O - S.C. - ring D, 100).
Oxyfunctionalization Products of Methyl 3-Oxo-5â-cholan-
3â-Acetoxy-5r-cholestan-25-ol (5c). 5c was isolated from the
reaction product of 5a as a colorless amorphous solid (Fr. 2)
crystallized from aqueous methanol; mp 124-126 °C (lit.,19 mp
1
124-126 °C); IR νmax/cm-1 3392 (OH), 1728 (CdO); H NMR
(32) Issidorides, C. H.; Fieser, M.; Fieser, L. F. J. Am. Chem. Soc. 1960,
82, 2002.
(33) Dalton, F.; McDougall, J. I.; Meakins, G. D. J. Chem. Soc. 1963, 4068.
(34) David, N. K.; Harold, C. T.; Christal, D.; Karen, A. W.; Kelvin, E.
S.; Shahid, L.; Robert, W. P. H. J. Chem. Soc., Perkin Trans. 2 1990, 1567.
J. Org. Chem, Vol. 72, No. 3, 2007 829

Iida et al.
(CDCl3) δ: 0.65 (3H, s, 18-CH3), 0.82 (3H, s, 19-CH3), 0.91 (3H,
d, J ) 6.8 Hz, 21-CH3), 1.21 (6H, s, 26- and 27-CH3), 2.02 (3H,
s, -COCH3), 4.68 (1H, brm, 3R-H); 13C NMR δ: 12.0 (C-18),
12.1 (C-19), 18.6 (C-21), 20.8 (C-23), 21.1 (C-11), 21.4 (OCOCH3),
24.1 (C-15), 27.4 (C-2), 28.2 (C-16), 28.5 (C-6), 29.1 (C-26), 29.3
(C-27), 31.9 (C-7), 34.0 (C-4), 35.4 (C-8 and C-10), 35.7 (C-20),
36.4 (C-22), 36.7 (C-1), 39.9 (C-12), 42.5 (C-13), 44.4 (C-24), 44.6
(C-5), 54.2 (C-9), 56.2 (C-17), 56.4 (C-14), 71.0 (C-25), 73.7 (C-
3), 170.6 (OCOCH3); LR-EI-MS m/z 428 (M - H2O, 14), 413 (M
- H2O - CH3, 8), 353 (M - AcOH - H2O - CH3, 15), 315 (44),
255 (44), 215 (M - AcOH - S.C. - ring D, 43), 95 (100).
script and providing useful comments. We also thank the Nihon
University Joint Research Subsidy for financial support in
2006.
Supporting Information Available: General experimental
information, materials, and methods. Analytical data for all products.
Table showing effects of a combination of metalloporphyrin-
catalyzed oxyfunctionalizations on the reactivity and regioselectivity
of substrate 3a. Table showing complete 1H and 13C chemical shifts
1
of 5R-oxygenated compounds 3c and 3d. Copies of H and 13C
NMR spectra of all compounds. This material is available free of
charge via the Internet at http://pubs.acs.org.
Acknowledgment. We thank Dr. Toshio Nambara, Professor
Emeritus, Tohoku University, for critically reading the manu-
JO061800G
830 J. Org. Chem., Vol. 72, No. 3, 2007