Immonium ion based synthetic methodology: a novel method for the N-methylation of dipeptides and amino acid derivatives via retro aza Diels-Alder reactions
Original proline or gamma-lactam derivatives bearing either an aryl group such as a phenyl or a 3-indolyl in position 3 of the proline moiety or on the 3-methyl chain of the gamma-lactam skeleton were prepared as nonpeptide mimics of Somatostatin/Sandostatin(R). (C) 1999 Elsevier Science Ltd. All rights reserved.
GRIECO, PAUL A.;BAHSAS, ALI, J. ORG. CHEM., 52,(1987) N 26, 5746-5749