Reduction of simple β-keto sulfides, β-keto sulfoxides and P-keto sulfones by an actively fermenting mutant of Saccharomyces cerevisiae proceeds readily and affords good yields of the corresponding optically active secondary alcohols. For example, 1-(benzylthio)propan-2-one gave optically pure (S)-(+)-1-(benzylthio)propan-2-ol and 1- (phenylsulfonyl)propan-2-one gave optically pure (S)-(+)-1- (phenylsulfonyl)propan-2-ol. In the reductions of racemic β-keto sulfoxides the enantiomers were reduced at sufficiently different rates to enable isolation of an optically active ketone and of an optically active β-hydroxy sulfoxide. Hence, 1-(phenylsulfinyl)propan-2-one gave (S)-(-)-1-(phenyl-sulfinyl)propan-2-one and (RS,SC)-(+)-1- (phenylsulfinyl)propan-2-ol.

α- and β-Keto esters and amides are readily reduced by an actively fermenting mutant of Saccharomyces cerevisiae and produce optically active α- and β-hydroxy esters and amides in moderate yields. Typically, methyl 2-oxo-2-phenylacetate gave methyl (R)-(-)-2-hydroxy- 2-phenyl- acetate; 2-oxo-2-phenylacetamide gave (R)-(-)-2-hydroxy-2- phenylacetamide; ethyl benzoylacetate gave ethyl (S)-(-)-3-hydroxy-3- phenylpropionate, and ethyl 2-oxocyclohexanecarboxylate gave ethyl (1R,2S)-(+)-2-hydroxycyclohexanecarboxylate. In each case, the product obtained was optically pure. However, the reduction of ethyl pyruvate to ethyl lactate produced partially racemized products.

The cyclodepsipeptide beauvericin and a mixture of the cyclodepsipeptides, enniatin Al, enniatin B,, enniatin B and enniatin A, have been isolated from plant pathogenic fungi. Previously, beauvericin has only been isolated from the unrelated entomopathogenic fungi.

The lipoamino acid serratamic acid has been isolated in considerable yield by alkaline extraction ofSerratia marcescens (Cartwright, 1955) and shown to consist of a linear amide of L-serine and D-3

S U M M A R YThe concentrations of lipid-bound serine (in the form of cyclic depsipeptide) and prodigiosin, in Serratia marcescens respond similarly to changes in environmental or cultural conditions so that highly pigmented cells always have a relatively large amount of lipid-bound serine. In addition, when prodigiosin synthesis is induced in non-pigmented cells, a parallel rapid synthesis of cyclic depsipeptide occurs concomitantly. Their simultaneous occurrence may indicate a common control.