The Molecular and Crystal Structure of the Glycopeptide A-40926 Aglycone

✍ Scribed by Martina Schäfer; Ehmke Pohl; Karen Schmidt-Bäse; George M. Sheldrick; Rolf Hermann; Adriano Malabarba; Marino Nebuloni; Giancarlo Pelizzi

• Publisher: John Wiley and Sons
• Year: 1996
• Tongue: German
• Weight: 507 KB
• Volume: 79
• Category: Article
• ISSN: 0018-019X
• DOI: 10.1002/hlca.19960790714

✦ Synopsis

Abstract

The crystal structure of a glycopeptide antibiotic A–40926 aglycone was investigated by X‐ray analysis at −120°. A‐40926 crystallises in the orthorhombic space group __P__2~1~2~1~2~1~ with two monomers in the asymmetric unit, a = 21.774(4), b = 28.603(7), c = 29.757(4) Å. ‘Conventional’ direct methods approach failed to solve the structure, but a novel iterative real/reciprocal space procedure was successful. Refinement against 11248 F^2^ data led to __R__1 = 13.3% for 6770 F > 4σ (F). The two monomers of A‐40926 have similar conformations and are bound by antiparallel H‐bonds to form a ‘chain’ structure of connecting dimers. The antibiotic molecule possesses a ‘binding pocket’ for the C‐terminal carboxy group of the cell‐wall protein, which is consisten with suggestions based on NMR data and the recently reported crystal structure of ureido‐balhimycin. In A‐40926 the monomers are polymerically linked by H‐bonds, quite unlike the tight dimer formation observed in ureido‐balhimycin.