Abstract: This invention relates to a process for the preparation of D(-) mandelic acid by the acid hydrolysis of the corresponding carbamate in an aqueous environment at a temperature of between 40.degree. and 100.degree. C. and at a pH of between 1 and 3.5.The invention also relates to a process for the enzymatic hydrolysis of racemic 5-substituted 2,4-oxazolidinediones to give only one of the two possible optical isomers, i.e., the D-carbamyl-.alpha.-hydroxy acid. The free D-.alpha.-hydroxy acid can be obtained from the optically active carbamyl derivative by simple hydrolysis. Of particular interest is the case in which the D-.alpha.-hydroxy acid is D(-)mandelic acid. The enzymatic activity required for preparing the carbamyl derivative of D(-)mandelic acid has been found both in homogenised veal liver and in a series of microorganisms, including Agrobacterium radiobacter, Bacillus brevis, Bacillus stearothermophilus, Pseudomonas sp., Pseudomonas desmolytica, Pseudomonas fluorescens, Pseudomonas putida.

Abstract: This invention relates to a process for preparing carbamyl derivatives of .alpha.-hydroxy acids by the hydrolysis of 5-substituted 2,4-oxazolidinediones.The carbamyl derivatives can be further hydrolyzed to .alpha.-hydroxy acids.The invention also relates to a process for the enzymatic hydrolysis of racemic 5-substituted 2,4-oxazolidinediones to give only one of the two possible optical isomers, i.e. the D-carbamyl-.alpha.-hydroxy acid. The free D-.alpha.-hydroxy acid can be obtained from the optically active carbamyl derivative by simple hydrolysis. Of particular interest is the case in which the D-.alpha.-hydroxy acid is D(-)mandelic acid. The enzymatic activity required for preparing the carbamyl derivative of D(-)mandelic acid has been found both in homogenized veal liver and in a series of microorganisms, including Agrobacterium radiobacter, Bacillus brevis, Bacillus stearothermophilus, Pseudomonas sp., Pseudomonas desmolytica, Pseudomonas fluorescens, Pseudomonas putida.

Abstract: In the preparation of 4-chloro-2-methyl-crotonaldehyde, an important starting material for the preparation of the acetate of Vitamin A, the improvement consisting in that isoprene monoepoxide (1:2-epoxy-2-methyl-3-butene) is chlorinated either with tert.butyl hypochlorite in the vapor phase, or with cupric chloride in the liquid phase. The reaction is preferably carried out in an inert siliceous or aluminous substrate at temperatures ranging from 60.degree. C to 150.degree. C. Lithium chloride has proven to be useful as a catalyst, but by no means essential.