Synthesis and properties of the stereoisomeric diethyl 2-aminocyclohexane-1,4-dicarboxylates
Abstract
Nucleophilic addition of ammonia to ethyl 4-cyanocyclohex-3-enecarboxylate (III), followed by hydrolysis and esterification yielded the four stereoisomeric diethyl 2-aminocyclohexane-1,4-dicarboxylates (I). The conformations of these isomers were established by n.m.r. spectroscopy and by stereospecific deaminations to give cyclohexenes or diethyl 2-hydroxycyclohexane-1,4-dicarboxylates (II). N- and O-Benzoyl derivatives of the cyclohexanecarboxylates (I) and (II) respectively are discussed in relation to deshielding effects on α-protons. Diethyl c-2-aminocyclohexane-r-1,c-4-dicarboxylate (Id) undergoes intramolecular cyclisation to give ethyl 7-oxo-6-azabicyclo[3.2.1]octane-4-carboxylate (X).