Scheme 2. HBPA Wild-Type and H205A Variant Catalyzed Aldol Addition of Pyruvate to Aldehydes 1 and Transformation of Aldol Adducts 3 into 3-Hydroxy Ester Derivatives 4, for Enantiomeric Ratio Measurement.

Conversions measured by HPLC.

HBPA wild-type.

Isolated yield.

ee not determined; the material was submitted directly to the enzymatic transamination reaction and the stereochemistry inferred from the corresponding 14c (for 3c), 15k (for 3k), 14n (for 3n), and 14o (for 3o) derivatives; see Schemes 7 and 8.

HBPA H205A variant.

The ee values were determined by HPLC on a chiral stationary phase.