Crystal structure of Boc-Ala-Aib-Ala-Aib-Aib-methyl ester, a pentapeptide fragment of the channel-forming ionophore suzukacillin

✍ Scribed by A. K. Francis; M. Iqbal; P. Balaram; M. Vijayan

• Publisher: Wiley (John Wiley & Sons)
• Year: 1983
• Tongue: English
• Weight: 387 KB
• Volume: 22
• Category: Article
• ISSN: 0006-3525
• DOI: 10.1002/bip.360220606

✦ Synopsis

Synopsis

t -Butyloxycarbonyl-~-alanyl-a-aminoisobutyryl-~-alanyl-a-aminoisobutyryl-a-aminoisobutyric acid methyl ester ( t -Boc-L-Ala-Aib-L-Ala-Aib-Aib-OMe), C24H43N508, an end-protected pentapeptide with a sequence corresponding to the 6th through the 10th residues in suzukacillin, crystallizes in the orthorhombic space group P212121 with a = 11.671, b = 14.534, c = 17.906 %,and z = 4. The molecule exists as a right-handed 3lo-helix with a pitch of 6.026

A. The helix is stabilized by three 4 -1 hydrogen bonds with the NH groups of Ala(3), Aib(4), and Aib(5) hydrogen bonding to the carbonyl oxygens of t-Boc, Ala(1). and Aib(2), respectively. The helical molecules arrange themselves in a head-to-tail fashion along the a direction in such a way that the NH groups of Ala(1) and Aib(2) hydrogen bond to the carbonyl oxygens of Aib(4) and Aib(5), respectively, of a translationally related molecule. The helical columns thus formed close-pack nearly hexagonally to form the crystal.