Carbocyclic alpha-amino acids: asymmetric synthesis of all four 1-amino-2-hydroxycyclohexanecarboxylic acids

Starting from racemic 2-methoxycyclohexanone and (S)- or (R)-1-phenylethyla mine, respectively, the four stereoisomers of 1-amino-2-hydroxycyclohexanec arboxylic acid are obtained via an asymmetric Strecker synthesis with ee va lues ranging from 87 to 98%. Their stereochemistry is established by NMR me thods and by X-ray analyses. Hydrogenolysis of a benzylic C-N bond by cone. sulphuric acid as well as cleavage of a methoxy ether by cone. HCl are two intriguing reactions which are observed within the five-step procedure des cribed herein. (C) 1999 Elsevier Science Ltd. All rights reserved.