Organic Process Research & Development 2011, 15, 279–283
Biocatalytic Resolution of Bis-tetrahydrofuran Alcohol
Yuri L. Khmelnitsky,*,† Peter C. Michels,† Ian C. Cotterill,† Michael Eissenstat,‡ Venkataiah Sunku,§
Venugopal R. Veeramaneni,§ Hariprasad Cittineni,§ Gopal R. Kotha,§ Shyamsunder R. Talasani,§ Krishna K. Ramanathan,⊥
Vakula K. Chitineni,⊥ and Bhaskar R. Venepalli⊥
AMRI Inc., Department of Metabolism and Biotransformations, 21 Corporate Circle, Albany, New York 12203, United States,
Sequoia Pharmaceuticals Inc., 401 Professional DriVe, Suite 200, Gaithersburg, Maryland 20879, United States, Indus
Biosciences PriVate Limited, Plot No. 72/A, Part 2, Phase-1, IDA Jeedimetla, Hyderabad 500 055, AP, India, and
CiVentiChem, 1001 Sheldon DriVe, Cary, North Carolina 27513, United States
Scheme 1
Abstract:
A simple and efficient process has been developed to effect the
kinetic resolution of the racemic alcohol 2 using immobilized lipase
to afford the desired optically pure (R)-bis-tetrahydrofuran (bis-
THF) alcohol 3, to facilitate the rapid progression of a clinical
candidate. Rapid optimization and development of reproducible
and scalable processes are essential to meet aggressive timeframes
for preclinical, safety, and early clinical drug development. Process
parameters were initially scoped and optimized using a combina-
tion of a rational bioprocess screening design and parallel micros-
cale empirical studies, specifically accounting for scale-up and
downstream processing considerations. The choices of reaction
solvent, acyl donor, and immobilized biocatalyst proved to be
critical factors in the design of a conveniently scalable and
enantioselective enzymatic resolution process. The improved
process was initially validated on 3-g and then 90-g scale in simple
impeller-stirred reactors, exhibiting excellent reproducibility. This
methodology was successfully implemented on a multikilogram
scale to give the target alcohol 3 with >99% ee.
alcohol (Scheme 1). In general, achieving both the desired
diastereoselectivity and enantioselectivity has remained a chal-
lenge, ultimately requiring additional steps and further enhance-
ment of chiral purity. We present here some of our investiga-
tions aimed at improving the resolution step for the scaled-up
synthesis of chiral alcohol 3, to facilitate the rapid progression
of SPI-256 as a clinical candidate.
The racemic form of the alcohol (2) was derived by reduction
of ketone 1.7 Lipase-catalyzed kinetic resolution promised to
be the most effective and practical route for achieving high
chiral purity of 3. A published biocatalytic procedure6 for
enantioselective acylation of 2 with acetic anhydride catalyzed
by Pseudomonas lipase in 1,2-dimethoxy ethane (DME) was
found to result in relatively low ee values for 3, modest
volumetric productivity, and modest yield due to overacylation
of the (R)-alcohol and challenging product isolation and
purification in our hands. Scale-up processes of this general
approach using lipases in DME have been reported but still
suffer from challenges in control of water activity for hygro-
scopic DME, modest ee, product isolation issues, and practical
process scale-up issues that ultimately necessitated the design
of a continuous reactor.4
Introduction
The synthetic intermediate (3R,3aS,6aR)-hexahydrofuro[2,
3-b]furan-3-ol, 3, is a key component for the synthesis of various
clinical HIV protease inhibitors (PIs) including darunavir,
brecanavir, GS-9005, and SPI-256.1-5 The bis-THF moiety has
imbued these PIs with high potency and excellent resistance
profiles. Not surprisingly, it has thus been the subject of
numerous synthetic investigations.1-4,6 The synthesis of the PIs
requires the enantiomerically pure (3R)-form 3 of bis-THF-
The goal of this work was to develop a more enantioselec-
tive, robust, and scalable biocatalytic process for kinetic
resolution of 2. An optimized process was developed to
successfully resolve and conveniently isolate both enantiomers
3 and 4 on a multikilogram scale.
* Corresponding author. E-mail yuri.khmelnitsky@amriglobal.com. Telephone
(518)-512-2890. Fax (518)-512-2078.
† AMRI Inc.
‡ Sequoia Pharmaceuticals Inc.
§ Indus Biosciences Private Limited.
Results and Discussion
⊥ CiVentiChem.
Optimization of Reaction Conditions. Catalyst EValuation.
Initially, several commercial immobilized Pseudomonas lipases
from Amano were tested, including PS-C I, PS-C II, PS-D I,
and AK-C I. The enzymes were immobilized on ceramic
particles (code “C” in the enzyme designation) or diatomaceous
earth (code “D”). The reactions were carried out in both DME
(1) Quaedflieg, P. J. L. M.; Kesteleyn, B. R. R.; Wigerinck, P. B. T. P.;
Goyvaerts, N. M. F.; Vijn, R. J.; Liebregts, C. S. M.; Kooistra,
J. H. M. H.; Cusan, C. Org. Lett. 2005, 7, 5917–5920.
(2) Canoy, W. L.; Cooley, B. E.; Corona, J. A.; Lovelace, T. C.; Millar,
A.; Weber, A. M.; Xie, S.; Zhang, Y. Org. Lett. 2008, 10, 1103–1106.
(3) Black, D. M.; Davis, R.; Doan, B. D.; Lovelace, T. C.; Millar, A.;
Toczko, J. F.; Xie, S. Tetrahedron: Asymmetry 2008, 19, 2015–2019.
(4) Yu, R. H.; Polniaszek, R. P.; Becker, M. W.; Cook, C. M.; Yu, L. H. L.
Org. Process Res. DeV. 2007, 11, 972–980.
(5) Erickson, J. W., Eissenstat, M., Silva, A. M., Afonina, E. I., Gulnik,
S. V. Poster H-1266; 48th Annual Interscience Conference on
Antimicrobial Agents and Chemotherapy (ICAAC), Washington, DC,
October 25-28, 2008.
(7) Ghosh, A. K.; Kincaid, J. F.; Walters, D. E.; Chen, Y.; Chaudhuri,
N. C.; Thompson, W. J.; Culberson, C.; Fitzgerald, P. M. D.; Lee, H. Y.;
McKee, S. P.; Munson, P. M.; Duong, T. T.; Darke, P. L.; Zugay, J. A.;
Schleif, W. A.; Axel, M. G.; Lin, J.; Huff, J. R. J. Med. Chem. 1996,
39, 3278–3290.
(6) Ghosh, A. K.; Chen, Y. Tetrahedron Lett. 1995, 36, 505–508.
10.1021/op100254z 2011 American Chemical Society
Published on Web 12/07/2010
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