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X‐Ray Crystal Structure of 25‐ O ‐Deacetyl‐27, 28‐didehydro‐27‐demthoxy‐11‐deoxo‐11, 29‐epoxy‐28,29‐dihydro‐21,23‐ O ‐isopropylidenerifamycin S
Author(s) -
Bartolucci Cecillia,
Cellai Luciano,
Cerrini Silvio,
Di Filippo Patrizia,
Lamba Doriano
Publication year - 1992
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.19920750112
Subject(s) - chemistry , stereochemistry , moiety , crystal structure , molecule , chromophore , epoxy , crystallography , organic chemistry
In search of new types of semisynthetic derivatives of the natural antibiotic rifamycin S ( 1 ), we synthesized 25‐ O ‐deacetyl‐27,28‐didehydro‐27‐demethoxy‐11‐deoxo‐11,29‐epoxy‐28, 29‐dihydro‐21,23‐ O ‐isopropyli‐denerifamycin S ( 3 ). Its X‐ray crystal structure shows a new type of ansa ‐chain with an 11,29‐epoxy moiety, the loss of the MeO group on C(27), and the shift of the CC bond from C(28),C(29) to C(27),C(28). These modifications result in a conformational rearrangement of the whole ansa ‐chain, nonetheless the overall spatial shape of the molecule is still close to that of most rifamycins. As found in other 11‐deoxo‐11‐hydroxyrifamycin‐S derivatives, the chromophore rings of 3 give rise to π‐π association in the crystal.