Baker's yeast mediated mono-reduction of 1,3-cyclohexanediones bearing two identical C(2) substituents

Article abstract of DOI:10.1016/S0957-4166(01)00015-5

Baker's yeast mediated transformation of a series of 1,3-cyclohexanediones with two identical substituents at C(2) was investigated and the results of the biotransformation were found to depend on the size of the substituents at C(2). 1,3-Cyclohexanediones with less sterically demanding C(2) substituents could be mono-reduced to provide the corresponding ketols in good yields and excellent enantiomeric excesses.

Full text of DOI:10.1016/S0957-4166(01)00015-5

TETRAHEDRON:
ASYMMETRY
Pergamon
Tetrahedron: Asymmetry 12 (2001) 229–233
Baker’s yeast mediated mono-reduction of 1,3-cyclohexanediones
bearing two identical C(2) substituents
Zhi-Liang Wei, Zu-Yi Li* and Guo-Qiang Lin*
Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 354 Fenglin Road, Shanghai 200032, China
Received 31 October 2000; accepted 20 December 2000
Abstract—Baker’s yeast mediated transformation of a series of 1,3-cyclohexanediones with two identical substituents at C(2) was
investigated and the results of the biotransformation were found to depend on the size of the substituents at C(2). 1,3-Cyclohex-
anediones with less sterically demanding C(2) substituents could be mono-reduced to provide the corresponding ketols in good
yields and excellent enantiomeric excesses. © 2001 Elsevier Science Ltd. All rights reserved.
1. Introduction
are valuable chiral intermediates in enantioselective nat-
ural product synthesis (R1"R2) (Scheme 1). However,
the microorganism mediated mono-reduction of 1,3-
cycloalkanediones with two identical C(2) substituents
to provide enantiomeric cycloalkanoid ketols is less well
known, and except for the simple substrate, 2,2-
dimethyl-1,3-cyclohexanedione 1,3 has not been investi-
gated. Since homochiral cycloalkanoid ketols are
potentially useful precursors in natural product synthe-
sis, we thought it worthwhile investigating the baker’s
yeast mediated biotransformation of 1,3-cycloalkane-
diones in more depth.
The baker’s yeast (Saccharomyces cerevisiae) mediated
asymmetric reduction of ketones has been widely used
to obtain chiral building blocks because it is cheap,
versatile and easy to perform.1 Brooks et al.2 have
successfully used baker’s yeast in the reduction of
prochiral 2,2-disubstituted 1,3-cycloalkanediones to
give ketol products with two stereogenic centers, which
2. Results and discussion
2,2-Disubstituted 1,3-cyclohexanediones 1,4 2,5 and 36
were prepared from their corresponding monosubsti-
Scheme 1.
Scheme 2.
* Corresponding authors. Tel.: 86-21-64163300; fax: 86-21-64166128; e-mail: lizy@pub.sioc.ac.cn
0957-4166/01/$ - see front matter © 2001 Elsevier Science Ltd. All rights reserved.
PII: S0957-4166(01)00015-5

230
Z.-L. Wei et al. / Tetrahedron: Asymmetry 12 (2001) 229–233
Table 1. Baker’s yeast mediated transformation of 1,3-cyclohexanediones 1–5
Entry
Substrate
R=
Product
Yielda (%)
[h]D
E.e. (%)
Config.
1
2
3
4
5
1
2
3
4
5
CH3
CH2CꢀCH
CH2CHꢁCH2
CH2CH2CH3
CH2CH2CO2CH3
6
7
8
9
10
48 (22)
41 (12)
14 (24)
<3 (25)
61
+22.5
−3.5
+11
–
>96b
>96c
98.4e
–
Sb
Sd
Sf
–
–
–
–
a Isolated yield; figure in the parentheses is the yield of recovered substrate.
b Based on the reported specific rotation.
c Determined by 1H NMR analysis of its Mosher ester.
d Determined by the improved Mosher method developed by Kusumi et al.
e Determined by chiral HPLC analysis.
f Assigned by X-ray crystallographic analysis of 12.
It can be seen from Table 1 that the baker’s yeast
mediated reduction of the 1,3-cyclohexanediones 1–5
depends strongly on the size of the two C(2) sub-
stituents. For the series propyl, allyl, propynyl and
methyl, there was a similar trend of increased reactivity
during baker’s yeast mediated reduction. 1,3-Cyclohex-
anediones with two less sterically demanding sub-
stituents, methyl or propynyl, at C(2) could be readily
reduced to afford ketols in high enantiomeric purity.
With increasing size of the C(2) substituents reactivity
diminished; hence, the relatively bulky allyl substituted
diketone 3 could be reduced, but the more bulky propyl
diketone 4 was much less reactive to baker’s yeast. The
limits of the system are shown in the reaction of
diketone 5, where no reduction occurred.
tuted 1,3-cyclohexanediones by introducing another
identical substituent at C(2) according to the reported
procedure. 2,2-Dipropyl-1,3-cyclohexanedione 4 was
prepared by catalytic hydrogenation of 3.6 The dicar-
boxylic ester 5 was readily prepared by Michael addi-
tion of the corresponding 2,6-dioxo-cyclohexane-
propanoic acid methyl ester7 with excess methyl acryl-
ate in triethylamine under reflux. The 1,3-cyclohexane-
dione derivatives 1–5 were then incubated with baker’s
yeast for 2 days (Scheme 2);8 the results of these
reactions are summarized in Table 1.
As shown in Table 1, 2,2-dimethyl-1,3-cyclohexane-
dione 1 and 2,2-di(prop-2-ynyl)-1,3-cyclohexanedione 2
could be well reduced by baker’s yeast to provide ketol
6 in a 48% yield with an e.e. of over 96%. Ketol 7 was
formed in 41% yield with excellent e.e. of over 96%
(Table 1, entries 1 and 2). The reduction of 1 using
bakers’s yeast was found to be similar to reported
results.3 Though baker’s yeast could still reduce the
dialkenic ketone 3 to provide ketol 8 in 14% yield with
e.e. of 98.4% (entry 3), incubation of 2,2-dipropyl-1,3-
cyclohexanedione 4 with baker’s yeast for 2 days pro-
vided only trace reduced product 9 (entry 4) and,
interestingly, when diketone 5 was incubated with bak-
er’s yeast for 2 days, the sole product obtained was
mono-hydrolyzed product 10 in a 61% yield (entry 5).
The effects of size of the two C(2) substituents on the
mono-reduction of 1,3-cyclohexanediones can be inter-
preted as follows. When both substituents at C(2) are
bulky, they ‘shield’ both faces of the two identical
prochiral carbonyl groups. Therefore, oxidoreductase(s)
in yeast cells might be prevented from approaching the
carbonyl groups and, as a result, cannot catalyze the
reduction efficiently. Therefore, if one of the C(2) sub-
stituents is less sterically demanding, for example a
methyl group, the steric hindrance on one side of the
cyclohexane plane would be lowered, which would
favor oxidoreductase(s) approaching one of the car-
bonyl groups from this side and reducing the corre-
The enantiomeric excess of 6 was determined by com-
sponding
2,2-disubstituted
1,3-cycloalkanedione
parison of its specific rotation with the reported value.3b
efficiently. This has been proved by the results of
1
The optical purity of 7 was determined by H NMR
analysis of its (R)-(+)-MTPA ester.9 The absolute
configuration of 7 was determined as (S) by the
improved Mosher method developed by Kusumi et al.10
using the MTPA esters of 7 (Scheme 3, Fig. 1).
The enantiomeric excess of 8 was directly determined
by chiral HPLC analysis detected at UV214 nm using its
racemic compounds as comparison. Its absolute
configuration was assigned by X-ray crystallographic
analysis after transformation into the corresponding
camphor sulfonate 12, by treatment with (+)-camphor-
10-sulfonyl chloride. As shown in Fig. 2, the configura-
tion of the hydroxymethylene carbon of
unambiguously established as (S).
8 was
Scheme 3. (i) (S)-(−)-MTPA, DCC, DMAP, CH2Cl2, rt, 12 h.
(ii) (R)-(+)-MTPA, DCC, DMAP, CH2Cl2, rt, 12 h.

Z.-L. Wei et al. / Tetrahedron: Asymmetry 12 (2001) 229–233
231
Figure 1.
Brooks et al.,2 who have successfully accomplished the
baker’s yeast mono-reduction of various 2,2-disubsti-
tuted 1,3-cycloalkanediones with a methyl group at
C(2).
3.1. Preparation of 3-[1-(2-methoxycarbonylethyl)-2,6-
dioxocyclohexyl]propionic acid methyl ester 5
A mixture of 3-(2,6-dioxocyclohexyl)propionic acid
methyl ester (3 g, 15 mmol),7 triethylamine (20 mL),
and methyl acrylate (15 mL) was refluxed for 20 h.
After cooling to room temperature, the mixture was
evaporated under reduced pressure to remove triethyl-
amine and excess methyl acrylate. The residue obtained
was purified by chromatography over silica gel with
petroleum ether–ethyl acetate (5:1) to provide 5 as
colorless oil (2.8 g, 65%). IR (KBr): wmax 2950, 1725
Considering the small coupling constants (<8.0 Hz) of
the protons geminal to the hydroxy groups, it is inter-
esting to find that the hydroxy groups of the obtained
ketol products 6–8 prefer the axial conformation. Fur-
thermore, after the hydroxy group was converted to the
corresponding carboxy group, it still prefers the axial
conformation. This could obviously be seen from the
X-ray analysis diagram of the camphorsulfonate 12
(Fig. 2). According to the studies of Gorthey et al.11
and Bowen et al.12 on conformational analysis of b-het-
eroatom-substituted cyclohexanones, the axial prefer-
ence of the hydroxy or the carboxy groups in 6–8 and
12 is probably due to the electrostatic or dipole–dipole
interactions which serve as stabilizing influences.
1
(br), 1695, 1435, 1370, 1180 (br), 1025, 850 cm−1. H
NMR (300 MHz, CDCl3): l 3.57 (s, 6H), 2.62 (t, 4H,
J=6.7 Hz), 2.20−2.10 (m, 4H), 2.05−1.90 (m, 6H). MS
m/z (rel. intensity): 284 (M+, 4.6), 221 (56.5), 192 (35.5),
164 (35.3), 151 (42), 137 (40.1), 55 (100), 42 (48.9).
Anal. calcd for C14H20O6: C, 59.14; H, 7.09. Found: C,
58.89; H, 7.23%.
3. Experimental
3.2. Baker’s yeast mediated transformation of 1−5.
General procedure
All melting points are uncorrected. IR spectra were
recorded on a Shimadzu IR-440 spectrometer. EI mass
spectra (MS) were run on an HP-5989 A mass spec-
trometer and high resolution mass spectra (HRMS)
were recorded on a Finnigan MAT-4021 instrument. 1H
NMR spectra were recorded on a Bruker AMX-300
spectrometer with tetramethylsilane as the internal stan-
dard. Optical rotation was measured on a Perkin–
Elmer 241 polarimeter. TLC was carried out using
HSG F254 silica gel plates and silica gel (200−400 mesh)
was used for chromatography. Organic extracts were
dried over anhydrous sodium sulfate. Baker’s yeast was
obtained from a local store.
A mixture of baker’s yeast (10 g) in 20% glucose
solution (50 mL) was shaken at 30°C for 1 h. The
substrate (1 mmol) in DMF (if it is solid, 0.5 mL) was
added slowly. The mixture was continuously shaken at
30°C for 2 days. After that baker’s yeast was removed
by centrifugation and washed with ethyl acetate. The
supernatant solution was saturated with sodium chlor-
ide and extracted with ethyl acetate (3×50 mL). The
organic layers were combined and washed with brine,
dried, filtered and evaporated under reduced pressure.
The residue was purified by chromatography to provide
the product as follows.
Figure 2. The molecular structure of 12.

232
Z.-L. Wei et al. / Tetrahedron: Asymmetry 12 (2001) 229–233
3.2.1. (S)-3-Hydroxy-2,2-di(prop-2-ynyl)cyclohexanone
7. White solid, mp 104−106°C; 96%, [h]2D0 −3.5 (c 2.0,
CHCl3). IR (KBr): wmax 3450, 3300, 2950, 1700, 1430,
1350, 1280, 1210, 1130, 1070, 1000, 945, 640, 560 cm−1.
1H NMR (300 MHz, CDCl3): l 4.18 (dd, 1H, J=6.2,
3.0 Hz), 2.80−2.50 (m, 5H), 2.50−2.30 (m, 2H), 2.10−
1.90 (m, 4H), 1.85−1.75 (m, 1H), 1.75−1.60 (m, 1H).
13C NMR (75 MHz, CDCl3): l 209.47, 79.85, 79.55,
73.87, 72.08, 71.81, 56.16, 37.84, 28.32, 22.92, 20.56,
19.97. Anal. calcd for C12H14O2: C, 75.76; H, 7.42.
Found: C, 75.69; H, 7.48.
7.52−7.38 (m, 5H), 5.53 (t, 1H, J=3.5 Hz), 3.51 (s, 3H),
2.86 (dd, 1H, J=7.0, 2.6 Hz), 2.75 (dd, 1H, J=7.5, 2.6
Hz), 2.60−2.46 (m, 2H), 2.38−2.29 (m, 2H), 2.18−2.03
(m, 4H), 1.85−1.77 (m, 1H), 1.70−1.60 (m, 1H). 13C
NMR (100 MHz, CDCl3): l 206.9, 165.7, 131.8, 129.9,
128.6, 127.5, 79.1, 78.2, 77.5, 77.3, 72.9, 72.7, 55.4, 54.1,
37.7, 24.9, 23.4, 20.6, 20.4.
3.4. Determination of the configuration of the ketol 8
To the solution of optically pure ketol 8 (20 mg, 0.1
mmol), obtained from baker’s yeast reduction of 3 in
methylene chloride (1 mL), and pyridine (0.5 mL) at
0°C was added (+)-camphor-10-sulfonyl chloride (120
mg, 0.5 mmol). The mixture was warmed to room
temperature and stirred for a day. After that the mix-
ture was diluted with ethyl acetate and the organic layer
was washed with brine, dried, filtered, and condensed.
Purification of the residue by chromatography with
petroleum ether–ethyl acetate (10:1) provided the corre-
sponding (+)-camphorsulfonates 12 (35 mg, 83%) as a
white solid: mp 90−91°C. [h]2D0 +43.6 (c 0.2, CHCl3). IR
(KBr): wmax 2973, 1738, 1709, 1446, 1339, 1175, 895, 870
3.2.2. (S)-2,2-Diallyl-3-hydroxycyclohexanone 8. White
solid, e.e.: 98.4%, [h]2D0 +11 (c 2.2, CHCl3). IR (KBr):
wmax 3450, 2940, 1685, 1640, 1340, 1275, 1215, 1110,
1
980, 920 cm−1. H NMR (300 MHz, CDCl3): l 5.70−
5.50 (m, 2H), 5.10−4.90 (m, 4H), 3.92 (dd, 1H, J=7.1,
3.1 Hz), 2.50−2.20 (m, 7H), 2.10−1.75 (m, 3H), 1.70−
1.50 (m, 1H). 13C NMR (75 MHz, CDCl3): l 212.39,
133.93, 133.47, 118.34, 118.06, 73.96, 57.46, 38.25,
36.82, 34.07, 28.23, 20.48. Anal. calcd for C12H18O2: C,
74.19; H, 9.34. Found: C, 73.88; H, 9.66. The enan-
tiomeric excess was determined by HPLC analysis using
Chiralpak AD column (0.46×25 cm) detected at UV
214 nm; eluent: hexane–2-propanol (9:1); rate of flow:
0.7 mL/min.
1
cm−1. H NMR (300 MHz, CDCl3): l 5.77−5.57 (m,
2H), 5.19−5.13 (m, 4H), 5.06 (dd, 1H, J=6.2, 3.7 Hz),
3.63 and 3.03 (AB, 2H, J=14.9 Hz), 2.60−2.27 (m, 9H),
2.14−1.93 (m, 4H), 1.88−1.75 (m, 1H), 1.68−1.61 (m,
2H), 1.49−1.43 (m, 1H), 1.13 (s, 3H), 0.88 (s, 3H). Anal.
calcd for C22H32O5S: C, 64.68; H, 7.89; S, 7.85. Found:
C, 64.66; H, 7.90; S, 8.07.
3.2.3.
3-[1-(2-Carboxylethyl)-2,6-dioxocyclohexyl]-
propionic acid methyl ester 10. White solid, mp 87−
89°C. IR (KBr): wmax 3400, 2900 (br), 1710 (br), 1450,
1
1410, 1330, 1290, 1210, 1170, 1030, 995, 910 cm−1. H
NMR (300 MHz, CDCl3): l 8.82 (br s, 1H), 3.70 (s,
3H), 2.90−2.50 (m, 4H), 2.50−2.20 (m, 4H), 2.20−1.90
(m, 6H). MS m/z (rel. intensity): 271 ([M+1]+, 12.7),
253 (33.9), 224 (45.2), 221 (100), 192 (54.7), 179 (44.2),
164 (38.2), 151 (52.4), 137 (45.2), 123 (38.5), 55 (78.3).
Anal. calcd for C13H18O6: C, 57.77; H, 6.71. Found: C,
57.45; H, 6.67.
Crystals of 12 suitable for X-ray analysis were cultured
from methylene chloride–petroleum ether. Data were
collected on a Rigaku AFC7R diffractometer using the
ꢀ−2q scan technique at 293 K. The intensities were
corrected for Lorentz-polarization effects. The structure
was solved by direct methods13 and expanded using
Fourier techniques.14 The non-hydrogen atoms were
refined anisotropically. Hydrogen atoms were included
but not refined. All calculations were performed using
the teXsan crystallographic software package.15 Crystal
data: colorless prismatic monoclinic crystal (0.20×0.20×
3.3. Determination of the absolute configuration of
ketol 7
,
To a stirred solution of 7 (15 mg, 0.14 mmol) in
methylene chloride (2 mL) was added dicyclohexylcar-
bodiimide (80 mg), 4-dimethylaminopyridine (3 mg),
and (R)-(+)-a-methoxy-a-(trifluoromethyl)phenyl acetic
acid (40 mg, 0.21 mmol). The mixture was stirred at
room temperature for 2 days, then filtered and the
filtrate was diluted with ethyl acetate (20 mL). The
organic phase was washed with saturated aqueous
sodium bicarbonate and brine, dried, filtered, and con-
densed under reduced pressure. The residue was
purified by chromatography over silica gel with
petroleum ether–ethyl acetate (7:1) to provide (R)-11
0.30 mm) in space group P21 (c4); a=11.204(2) A,
,
,
b=7.9105(9) A, c=13.093(3) A, i=111.86(1)°, V=
3
1077.0(3) A ; Z=2; Dcalcd=1.260 g cm−3; F(000)=
,
440.00; Mo Kh (u=0.71069 A), v=1.79 cm−1;
reflections measured=2769, unique reflections=2641
(Rint=0.015); observations [I>2|(I)]=2236; parame-
ters=253; goodness-of-fit=1.68; R=0.041, Rw=0.047.
,
Acknowledgements
1
(30 mg, 94%). H NMR (300 MHz, CDCl3): l 7.53−
The authors are grateful to the National Natural Sci-
ence Foundation of China (Grant No. 39770020) for
financial support.
7.39 (m, 5H), 5.60 (dd, 1H, J=5.2, 3.0 Hz), 3.51 (s,
3H), 2.86 (dd, 1H, J=6.9, 2.5 Hz), 2.71 (dd, 1H,
J=7.5, 2.6 Hz), 2.63−2.37 (m, 2H), 2.29−2.16 (m, 2H),
2.13−2.03 (m, 4H), 1.94−1.80 (m, 2H). MS m/z (rel.
intensity): 407 ([M+1]+, 0.7), 406 (M+, 0.4), 189 (100).
References
(S)-11 was similarly prepared according to the above
1. For reviews, see: (a) Csuk, R.; Glanzer, B. I. Chem. Rev.
1991, 91, 49. (b) Sevi, S. Synthesis 1990, 1. (c) Santaniello,
1
procedure, yield 90%. H NMR (300 MHz, CDCl3): l

Z.-L. Wei et al. / Tetrahedron: Asymmetry 12 (2001) 229–233
233
E.; Ferraboschi, P.; Grisenti, P.; Manzocchi, A. Chem.
Rev. 1992 92, 1071.
no reduced product was isolated.
9. The (R)-(+)-MTPA ester derived from racemic 7 showed
2. (a) Brooks, D. W.; Grothaus, P. G.; Irwin, W. L. J. Org.
Chem. 1982, 47, 2820; (b) Brooks, D. W.; Grothaus, P.
G.; Palmer, J. T. Tetrahedron Lett. 1982, 23, 4187; (c)
Brooks, D. W.; Grothaus, P. G.; Mazdiyasni, H. J. Am.
Chem. Soc. 1983, 105, 4472; (d) Brooks, D. W.;
Mazdiyasni, H.; Chakrabarti, S. Tetrahedron Lett. 1984,
25, 1241; (e) Brooks, D. W.; Mazdiyasni, H.; Sallay, P. J.
Org. Chem. 1985, 50, 3411; (f) Brooks, D. W.; Woods, K.
W. J. Org. Chem. 1987, 52, 2036; (g) Brooks, D. W.;
Mazdiyasni, H.; Grothaus, P. G. J. Org. Chem. 1987, 52,
3223.
two signals at 5.53 and 5.61 ppm, while only the signal
at 5.53 ppm was observed in the H NMR spectrum of
the (R)-(+)-MTPA ester of 7. Therefore, the e.e. of 7
obtained from baker’s yeast mono-reduction of 2 was
considered to be over 96% e.e.
1
10. Ohtani, I.; Kusumi, T.; Kashman, Y.; Kakisawa, H. J.
Am. Chem. Soc. 1991, 113, 4092.
11. (a) Gorthey, L. A.; Vairamani, M.; Djerassi, C. J. Org.
Chem. 1985, 50, 4173; (b) Lu, Y.; Barth, G.; Kieslich, K.;
Strong, P. S.; Duax, W. L.; Djerassi, C. J. Org. Chem.
1983, 48, 4549.
3. (a) Yanai, M.; Sugai, T.; Mori, K. Agric. Biol. Chem.
1985, 49, 2373; (b) Mori, K.; Mori, H. Organic Synthesis;
Wiley: New York, 1990; Vol. 68, p. 56; (c) Mori, K.;
Mori, H.; Yanai, M. Tetrahedron 1986, 42, 291.
4. Swaminathan, S.; Ramachandran, S.; Sankarappa, S. K.
Tetrahedron 1963, 20, 1119.
5. Schulte, K. E.; Reisch, J.; Mock, A. Arch. Pharm. 1962,
295, 645.
6. Chem. Abstr. 1969, 73, 24971a.
12. Bowen, J. P.; Allinger, N. L. J. Org. Chem. 1987, 52,
1830.
13. Sheldrick, G. M. In Crystallographic Computing 3;
Sheldrick, G. M.; Kruger, C.; Goddard, R., Eds.
SHELXS-86. Oxford University Press, 1985; p. 175.
14. The DIRDIF Program System, Technical Report of Crys-
tallography Laboratory; Beurskens, P. T.; Admiraal, G.;
Beurskens, G.; Bosman, W. P.; Garcia-Granda, S.;
Gould, R. O.; Smith, J. M. M.; Smykalla, C., Eds.
DIRDIF-92. University of Nijmegen: The Netherlands,
1992.
7. Konno, M.; Nakae, T.; Sakuyama, S.; Imaki, K.; Nakai,
H.; Namanaka, N Synlett 1997, 1472.
8. It is noteworthy that when the C(2) monosubstituted
1,3-cyclohexanedione was incubated with baker’s yeast
15. teXsan: Crystal Structure Analysis Package; Molecular
Structure Corporation: London, 1992.
.