Preferred solution conformation of peptides rich in the lipophilic, chiral, C-alpha-methylated alpha-amino acid (alpha Me)Aoc

The lipophilic, chiral, C-alpha-methylated alpha-amino acid L-(alpha Me)Aoc (2-methyl-2-amino-octanoic acid) was prepared using a chemo-enzymatic appr oach. Two series of terminally protected model peptides, from dimer through to hexamer, containing L-(alpha Me)Aoc in combination with either Gly or A ib, were synthesized by solution methods and were fully characterized, A so lution conformational analysis, based on FT-IR absorption, H-1-NMR and circ ular dichroism (CD) techniques, was performed with the aim at determining t he preferred conformation of this novel amino acid and the relationship bet ween chirality at its cc-carbon atom and screw sense of the helix that is f ormed. The results obtained strongly support the view that L-(alpha Me)Aoc favours the formation of the right-handed 3(10)-helical conformation. Copyr ight (C) 1999 European Peptide Society and John Wiley & Sons, Ltd.