title: An Efficient Strategy to Orthogonally Protected (R)- and (S)-alpha-Methyl(alkyl)serine-Containing Peptides via a Novel Azlactone/Oxazoline Interconversion Reaction.
abstract: A novel strategy for the synthesis of (R)- and (S)-alpha-methyl(alkyl)serine-containing peptides is presented. Using (S)-phenylalanine cyclohexylamide 6 as chiral auxiliary, the optically pure azlactones (R)- and (S)-2 were synthesized via a novel azlactone/oxazoline interconversion reaction (Figures 3 and 6). These azlactones constitute fully protected and activated synthetic equivalents of (R)- and (S)-alpha-methylserine and can be directly incorporated into peptides without further protective group manipulations. Like other alpha,alpha-dialkylated glycines, optically pure alpha-alkylserines can be used to stabilize beta-turn and alpha-helical conformations in short peptides.
authors.affiliation: Pharma Research, F. Hoffmann-La Roche AG, CH-4070 Basel, Switzerland.
authors.forename: Daniel
authors.initials: D
authors.lastname: Obrecht
authors.forename: Michael
authors.initials: M
authors.lastname: Altorfer
authors.forename: Christian
authors.initials: C
authors.lastname: Lehmann
authors.forename: Peter
authors.initials: P
authors.lastname: Schönholzer
authors.forename: Klaus
authors.initials: K
authors.lastname: Müller