A flexible route to chiral 2-endo-substituted 9-oxabispidines and their application in the enantioselective oxidation of secondary alcohols.

A new and flexible route to enantiomerically pure bi- and tricyclic 9-oxabispidines has been developed with use of (1R,5S)-7-methyl-2-oxo-9-oxa-3,7-diazabicyclo[3.3.1]nonane-3-carboxylic acid tert-butyl ester as the common late-stage intermediate. The 9-oxabispidines synthesized were evaluated as the chiral ligands in the Pd(II)-catalyzed oxidative kinetic resolution of secondary alcohols giving good to excellent selectivity factors of up to 19.

Enantioselective synthesis of tricyclic amino acid derivatives based on a rigid 4-azatricyclo[5.2.1.0]decane skeleton.

An enantioselective route to four tricyclic amino acids and N-tosylamides, composed of a central norbornane framework with a 2-endo,3-endo-annelated pyrrolidine ring and a 5-endo-C1 or -C2 side chain, has been developed. A key intermediate was the chiral, N-Boc-protected ketone (1R,2S,6S,7R)-4-azatricyclo[5.2.1.0²,6]decan-8-one, available from inexpensive endo-carbic anhydride in five steps and 47% yield. The rigid scaffold makes these amino acid derivatives promising candidates for beta-turn-inducing building blocks in peptidomimetics and for chiral auxiliaries in asymmetric organocatalysis.