New synthesis of all four 1-amino-2-hydroxycyclohexanecarboxylic acids

This report describes a new synthesis of the four stereoisomers of 1-amino-2-hydroxycyclohexanecarboxylic acids [(1S,2S)-, (1R,2R)-, (1S,2R)- and (1R,2S)-c6Ser], four conformationally constrained serine (Ser) analogues, possessing a six-membered carbocyclic ring. Initially, we synthesised cis-c6Ser and trans-c6Ser in their racemic forms, using as key steps the Diels–Alder reactions of methyl 2-benzamidoacrylate with Danishefskyʹs diene and 1-methoxy-1,3-butadiene, respectively. The optically active forms were achieved by resolution methods.