Vibrational spectra of N-acetylglycine oligomers Part 2.—Raman scattering study of selectively C-deuteriated oligomers with polyglycine I- and II-type structures
Selectively C-deuteriated N-acetylglycine trimer and
tetramer acid types have been synthesized, and their two crystalline
modifications, solid-A and solid-B [which correspond in structure to
polyglycine (PG) II and I, respectively] have been prepared. Raman
scattering spectra have been measured for a series of these glycine
oligomers, and the CH
2
- and CD
2
-characteristic
modes have been investigated in detail. Assignment of the
CH
2
-characteristic bands to each CH
2
group in
the oligomers has been carried out successfully. In particular, the
results obtained from the CD
2
stretch region show that N-
and C-terminal glycine residues for the PGI- and PGII-type trimers and
tetramers are all in very similar environments and that the glycine
residues which are sandwiched between the two terminal residues are
also in a similar environment for both the trimers and the tetramers.
The syntheses and properties of p-nitrobenzyl diazoacetyl-glycinate (VI), p-nitrobenzyl p-(p-methoxyphenylazo)-benzyloxycarbonyl-glycyl-glycollyl-glycinate (II) and p-nitrobenzyl p-phenylazo-benzyloxycarbonyl-glycyl-glycollyl-glycinate are described. These compounds have been prepared as intermediates for the synthesis of other depsipeptides.