Stereocontrolled Preparation of Diversely Trifunctionalized Cyclobutanes

The
expedient and stereoselective syntheses of small libraries of trifunctionalized
cyclobutane scaffolds bearing an acid, an amine, and a third functional
group are described. Starting from a single precursor, the readily
available protected derivative of all-cis-2-amino-3-hydroxycyclobutane-1-carboxylic
acid, cis-trans stereoisomers are obtained following
an SN2-type reaction, while all-trans stereoisomers
are obtained using the same strategy preceded by a C1 epimerization
reaction.