The invention provides novel aldolases, nucleic acids encoding them and methods for making and using them, including chemoenzymatic processes for making .beta.,.delta.-dihydroxyheptanoic acid side chains and compositions comprising these side chains, e.g., [R-(R*,R*)]-2-(4-fluorophenyl)-b,d-dihydroxy-5-(1-methylethyl)-3-phenyl-4- -(phenylamino)-carbonyl]-1H-pyrrole-1-heptanoic acid (atorvastatin, LIPITOR.TM.), rosuvastatin (CRESTOR.TM.), fluvastatin (LESCOL.TM.), related compounds and their intermediates.