M. Marchini, M. Mingozzi, R. Colombo
Dec 4, 2010
Citations
0
Influential Citations
7
Citations
Journal
Tetrahedron
Abstract
Abstract The synthesis of two diastereomeric cyclo[Asp- N -Bn-Ser] diketopiperazines ( 2a and 2b ) was investigated. Initial formation of the Boc-aspartyl- N -benzyl serine isopeptide methyl esters ( 4a and 4b ) was observed, which derive from the selective O-acylation of unprotected ( S )- or ( R )- N -benzylserine. This unexpected O-acylation is preferred over the formation of the tertiary amide and the resulting ester bond is stable in solution to O , N -acyl transfer. The O , N -acyl migration is then triggered by cleavage of the Boc protecting group and treatment with base, which also promotes immediate cyclization to the diketopiperazines.