Stereoselective acylation of racemic hydroxyalkylsilanes 102 was achieved using a crude papain preparation and, surprisingly, 4-phenylpentanoic acid as the acyl donor. The ees of the products 103 and the recovered substrates varied from 30 to 99% (Equation 49).115

R1 Si (CH2)„ OH P^^pa|nCO?H * R1 Si (CH2)„ OH + R1 Si (CH2)„ OC(CH2)4Ph (48)

In turn, a lipase-promoted acylation of prochiral substrates 104, using lipases from Candida cylinracea and Chromobacterium viscosum and methyl isobutyrate or acetoxime isobutyrate as the acyl donors, gave the product 105 in yields up to 80% and with ees up to 75% (Equation 50).116

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