Methyl substituted cyclohexyl-1-amino-3-hydroxy-1-carboxylic acid derivativ
es have been prepared from 5,5-tethered dienes of (2R)-2,5-dihydro-2-isopro
pyl-3,6-dimethoxypyrazine in stereoselective syntheses. Ring closing metath
esis reaction of the diene 2 afforded a heterospirenone which was the subst
rate for conjugate addition with an alkyl cuprate. Reduction of the adduct
followed by hydrolytic cleavage of the heterocyclic ring provided a cyclic
a-amino acid derivative. The absolute configuration at the new stereocenter
s in the products were established by X-ray crystallography analyses. (C) 2
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