CRYSTAL-STRUCTURE ANALYSIS OF A BETA-TURN MIMIC IN HYDRAZINO PEPTIDES

The crystal structures of four hydrazino peptides (Piv-Pro-h(N-alpha-B zl)Gly-NHiPr 1, Piv-Pro-hAla-NHiPr 2, Mcc-hPro-NHiPr 3, and Boc-hPro-G ly-N(OH)Me 4) deriving from the hydrazino analogues of glycine (hGly), L-alanine (hAla) or L-proline (hPro) have been solved. They reveal a common folded structure of the alpha-hydrazino acid residue characteri zed by a bifurcated hydrogen bond closing an eight-membered cycle. Thi s folded structure is topologically similar to the beta II'-turn in pe ptides, and the CO-NH-N hydrazide link can be considered as a good tur n-inducer in peptide analogues. (C) Munksgaard 1994.