STRUCTURAL VERSATILITY OF PEPTIDES FROM C-ALPHA,ALPHA-DISUBSTITUTED GLYCINES - SYNTHESIS, CHARACTERIZATION, AND SOLUTION CONFORMATIONAL-ANALYSIS OF HOMOPEPTIDES FROM C-ALPHA-METHYL-C-ALPHA-BENZYLGLYCINE, [(ALPHA-ME)PHE]N(1)
M. Pantano et al., STRUCTURAL VERSATILITY OF PEPTIDES FROM C-ALPHA,ALPHA-DISUBSTITUTED GLYCINES - SYNTHESIS, CHARACTERIZATION, AND SOLUTION CONFORMATIONAL-ANALYSIS OF HOMOPEPTIDES FROM C-ALPHA-METHYL-C-ALPHA-BENZYLGLYCINE, [(ALPHA-ME)PHE]N(1), Macromolecules, 26(8), 1993, pp. 1980-1984
A complete series of N- and C-blocked, monodispersed homooligopeptides
from the sterically hindered (alpha-Me)Phe residue to the pentamer le
vel was synthesized step-by-step by solution methods and fully charact
erized. The preferred conformation in chloroform solution was determin
ed by FT-IR and H-1 NMR as a function of concentration and addition of
a perturbing agent. In particular, the results obtained strongly supp
ort the view that a series of three consecutive beta-turns (3(10)-heli
x) is preferentially adopted by the pentamer, a clear indication that
the (alpha-Me)Phe residue is an efficient beta-turn and helix former,
much stronger than its unmethylated parent compound (Phe). A compariso
n is also made with the conclusions extracted from a published work on
homopeptides from Aib, the prototype of C(alpha,alpha)-disubstituted
glycines.