Dedicated to Professor H. Ila on her 80th birthday
A highly efficient, multi-gram scale asymmetric synthesis of 3,3′-pyrrolidonyl spirooxindole-5′-carboxylic
ester, which could be a potential precursor for the synthesis of cyanogramide, is
accomplished from commercially available l-1-methyltryptophan in two pots. Fluoride-promoted desilylative spiro-cyclization
of (semi) in situ generated isocyanate derived from l-1-methyltryptophan is the key reaction. Further, a variety of arene-substituted 3,3′-pyrrolidonyl
spirooxindole-5′-carboxylxic acid esters were synthesized by late stage functionalization
of easily accessible 3,3′-pyrrolidonyl spirooxindole-5′-carboxylic ester.
Key words
spirooxindole - asymmetric synthesis - fluoride-promoted - desilylative - spirocyclization
- tryptophan - cyanogramide - 3,3′-pyrrolidonyl spirooxindole
