Structural biochemistry. Part VIII. 9-Amino-(9-deoxy)-cinchona alkaloids

Abstract

Lithium aluminum hydride reduction of the oximes derived from quinidinone (IIIa) and cinchonidinone has been used to obtain 9-amino-(9-deoxy)quinidine (IIb) and the corresponding 9-amine in the cinchonine series. Based on optical rotatory dispersion measurements, tentative stereochemical assignments for the amines have been proposed. A major objective of the present study, synthesis of 9-(benzyloxycarbonylthreonylseryl)amino-(9-deoxy)quinidine (IId) was achieved by condensing amine (IIb) with benzyloxycarbonylthreonylserine azide. In connection with the preparation of quinidinone and cinchonidinone, reaction between, e.g., quinine and acetic anhydride–dimethyl sulphoxide gave exclusively the corresponding 9-acetoxy-derivative.