E. Pinot et al. / Tetrahedron: Asymmetry 16 (2005) 1893–1895
1895
2
D
0
ꢁ2
Table 2. ½aꢀ (c 1 · 10 , MeOH) for alcohols 2 and 3 and acetates 8
(a)
and 9
(
(
R)-2
R)-8
+0.21
ꢁ0.05
ꢁ0.21
(S)-3
(S)-9
(
R)-8
(S)-9
+0.05
(R)-2
(S)-3
6
ing Mosher esters (Fig. 2). We also confirmed these ee
by H NMR experiments (data not shown).
1
1
5 h.
(b)
2
0 h.
(c)
0
21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46
19
Figure 2. F NMR spectra of alcohols (S)-3 and (R)-2.
Figure 1. (a) Chromatogram of a racemic mixture of acetates 8, 9 and
alcohols 2, 3. (b) and (c) Chromatograms of the kinetic resolution of
rac-1 by CAL-B after 15 h (b) and 20 h (c). Column: Chiralcel OD,
3. Conclusion
25 cm · 4.6 mm. Mobile phase: 97/3 hexane/i-PrOH. Flow rate:
0.7 mL/min. Detection : 210 nm.
In conclusion, we have developed an efficient asymmet-
ric synthesis of the two enantiomerically pure hydroxy-
cyclopentenones (R)-2 and (S)-3. The extension of this
methodology towards the synthesis of new isoprostanes
will be reported in due course.
monitored by TLC and the enantiomerically pure (R)-
alcohol 2 obtained in 98% yield.
O
O
CO2Me
OMe
CO Me
Acknowledgments
2
a
OMe
We wish to thank the Minist e` re de lÕEducation Natio-
nale, de lÕEnseignement Sup e´ rieur et de la Recherche
for financial support to E.P.
AcO
HO
MeO
R)-8
MeO
(R)-2
(
3
Scheme 3. Reagents and conditions: (a) CAL-B, CH CN, phosphate
buffer (0.1 M) pH = 7.
References
1
. Bornscheuer, U. T.; Kazlauskas, R. J. Hydrolases in
Organic Synthesis—Regio- and Stereoselective Biotransfor-
mations; Wiley-VCH: Weinheim, 1999.
2.4. Comparison of the specific rotations of 2 and 3, and 8
and 9
2
. Rodriguez, A. R.; Spur, B. W. Tetrahedron Lett. 2003, 44,
7411–7415.
Acetate 9 was obtained from alcohol 3 with (Ac) O in
2
Et O in the presence of DMAP in 74% yield.
2
3. For a general review, see: Chem. Phys. Lipids 2004, 128,
–193.
4
1
. (a) Loza, E.; Lola, D.; Freimanis, J.; Turovskis, I.; Gavars,
M.; Liepipa, A. Latvijas PSR ZA vestis, Chem. Ser. 1985, 4,
The physicochemical properties of the enantiomerically
pure alcohol (R)-2 and acetate (R)-8 were identical to
those of (S)-3 and (S)-9, respectively, except for the sign
of the specific rotation, as shown in Table 2.
465–472; (b) Loza, E.; Lola, D.; Freimanis, J.; Leipina, A.
Latv. Kim. Z. 1998, 1, 76–82.
5
. Babiak, K. A.; Ng, J. S.; Dygos, J. H.; Weyker, C. L.;
Wang, Y.-F.; Wong, C.-H. J. Org. Chem. 1990, 55, 3377–
2
.5. Determination of the ee
3
2
381; For a general review, see: Tetrahedron: Asymmetry
004, 15, 2727–3009.
The ee of alcohol (S)-3 (94%) and (R)-2 (94%) was deter-
mined by F NMR spectra analysis of the correspond-
6. Dale, A. J.; Dull, D. L.; Mosher, H. S. J. Org. Chem. 1969,
34, 2543–2549.
1
9