Regio- and stereoselective synthesis of the enantiomers of monoterpene-based β-amino acid derivatives

The regio- and stereospecific addition of chlorosulfonyl isocyanate to cis-delta-pinene enantiomers has furnished monoterpene-fused beta-lactams. The observed regioselectivity can be explained by ab initio DFT modeling of transition state structures. In contrast with the less reactive alpha-pinane-fused beta-lactam 4, the resulting beta-lactams 5 and 13 containing an amino group connected to a secondary carbon possess similar reactivity to the cycloalkane-fused analogues and can be easily converted to the beta-amino acid and its protected derivatives. The base-catalyzed isomerization of the cis-amino ester afforded the corresponding trans-amino ester in moderate yield. (c) 2007 Published by Elsevier Ltd.