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Crystal Structure and Packing of Isocyclosporin A
Author(s) -
Pohl Ehmke,
Sheldrick George M.,
Bölsterli Johann J.,
Kallen Jörg,
Traber René,
Walkinshaw Malcolm D.
Publication year - 1996
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19960790614
Subject(s) - chemistry , crystal structure , orthorhombic crystal system , crystallography , intermolecular force , amide , crystal (programming language) , stereochemistry , residue (chemistry) , molecule , organic chemistry , computer science , programming language
The crystal structure of isocyclosporin A ( 1 ), a rearrangement product of the immunosuppressant drug cyclosporin A, has been determined at 193 (2) K. Crystals are orthorhombic with cell dimensions a = 26.684 (7), b = 26.936 (3) Å, c = 28.549 (7) Å, space group C 222 1 . The structure was solved by direct methods and refined by full‐matrix least‐squares methods to a conventional R value of 0.110. In contrast to the structure of cyclosprin A in solution and in the crystal, isocyclosporin A ( 1 ) has no regular secondary structural elements. The backbone adopts an open, irregular conformation with cis amide bonds between residue 2 and 3, and 3 and 4, respectively. All the other amide bonds and the ester linkage are trans. Contrary to crystal structures of cyclosporin derivatives, this crystal structure is stabilized by two transannular and four intermolecular H‐bonds.