No abstract

Both enantiomers of biologically and pharmaceutically interesting benzofuran‐, benzothiophen‐, and phenylfuran‐based 1‐heteroarylethanamines were prepared at close to theoretical yields by using Candida antarctica lipase B (Novozym 435) catalyzed (R)‐selective N‐acylation with isopropyl butanoate (enantiomeric ratio E > 200). The use of N‐methyl‐2‐pyrrolidinone (NMP) as a cosolvent (1:30) in isopropyl butanoate solved the problem of low solubility of the compounds. Instability of the heterocyclic ring systems against traditional acid‐ and base‐catalyzed hydrolysis was solved by using Candida antarctica lipase A as a commercial CAL‐A‐CLEA preparation for deprotection of the N‐acylated (R) enantiomers in water. The slow, highly enantioselective (E > 200) hydrolyses of racemic butanamides was also observed in the presence of Novozym 435.

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The kinetic resolution of three dorzolamide intermediates has been studied in the presence of Burkholderia cepacia lipase in organic solvents. All the stereoisomers of 6-methyl-5,6-dihydro-4H-thieno[2,3-b]thiopyran-4-ol were prepared starting from the racemic cis-dihydrothiopyranol intermediate giving first the 4R,6S and 4S,6R enantiomers. Subsequent epimerization and purification of the trans enantiomers by enzymatic acylation or alcoholysis then gave the cis enantio-

Sulphur heterocyclic β-hydroxy nitriles are prepared from the suitable aldehyde and (trimethylsilyl)acetonitrile in the presence of lithium acetate at good yields. Burkholderia cepacia lipase allowed the formation of the both enantiomers of β-hydroxy nitriles in highly enantiopure forms (ee 99%) through acylation of a racemic mixture and alcoholysis of the acylated enantiomer in tert-butyl methyl ether.