Selective biotransformation reactions on (±)-aryl alkyl ketones,
(±)-benzoxazines, and D-arabino-
and D-threo-hydroxyalkyltriazoles*
Raunak, Ashok K. Prasad, Najam A. Shakil, Himanshu, and Virinder S.
Parmar**
Department of Chemistry, University of Delhi, Delhi-110
007, India
Abstract: The capabilities of porcine pancreatic lipase (PPL),
Candida antarctica lipase (CAL), and Candida rugosa lipase
(CRL) were evaluated for enantio- and/or regioselective acetylation/deacetylation
of (±)-2,4-diacetoxyphenyl alkyl ketones, (±)-4-alkyl-3,4-dihydro-3-hydroxyalkyl-2H-1,3-benzoxazines,
and D-arabino and D-threo-polyhydroxyalkyltriazoles
in organic solvents. PPL in tetrahydrofuran (THF) exhibited high to
moderate enantioselectivity during the deacetylation of (±)-2,4-diacetoxyaryl
alkyl ketones and acetylation of (±)-3-hydroxyalkyl-2H-1,3-benzoxazines.
Together with enantioselectivity, PPL in THF also showed exclusive regioselectivity
for the deacetylation of para-acetoxy over the ortho-acetoxy
function, with respect to the nuclear carbonyl group in 2,4-diacetoxyphenyl
alkyl ketones. CAL in diisopropyl ether (DIPE) and PPL in THF exhibited
exclusive selectivity for the acetylation of primary hydroxyl over secondary
hydroxyl group(s) of D-arabino- and D-threo-polyhydroxyalkyltriazoles.
* Lectures presented at the International Symposium
on Green Chemistry, Delhi, India, 10-13 January 2001. Other presentations
are published in this issue, pp. 77-203.
** Corresponding author.
