Olga Sarre

Synthesis of the antifungal agent sch 424271 (SM 9164)

Abstract A chiral synthesis of the antifungal agent Sch 42427 starting from S-chloropropionic acid is described.

Structure elucidation of everninomicin-6, a new oligosaccharide antibiotic, by chemical degradation and FAB-MS methods

The structural characterization of a new oligosaccharide antibiotic, Everninomicin-6 (EV-6), is described. Detailed fast-atom bombardment mass spectrometry (FAB-MS) studies along with NMR and chemical degradation methods were conducted to elucidate the structure of EV-6. The effects of the use of various matrices, including salt addition, on the quality of the FAB-MS were explored. The use of 3-nitro benzyl alcohol, dimethyl sulfoxide (DMSO), and NaCl produced the best results: an intense sodiated molecular ion plus structurely informative fragmentation. FAB-MS yields information providing the complete sugar sequence information for everninomicins, which is quite valuable to the elucidation of the structure of this complex oligosaccharide antibiotic. In addition, the results of accurate mass work with the molecular ion are consistent with the assigned structure. The use of electrospray ionization mass spectrometry (ESI-MS) and ESI-MS/MS for the study of EV-6 was investigated and was found to produce an abundant molecular ion with limited structural information. These results revealed that EV-6 resembled EV-D quite closely except for the absence of the nitrosugar and the replacement on ring g of the -CH2OCH3 group with a -CH2OH group.

Stereochemistry at C-3 of evernitrose: a fallacy in the determination of stereochemistry at quaternary centres using nuclear magnetic resonance spectroscopy. X-Ray crystal structure of methyl 3-acetamido-2,3,6-trideoxy-3-c,4-O-dimethyl-L-xylo-hexopyranoside

Single crystal X-ray analysis of the title compound (8) is reported which establishes the stereochemistry at C-3 of evernitrose.

Structure of halomicin B

The antibiotic halomicin B has been shown by spectroscopic and chemical means to have the structure (1).

Structure and absolute stereochemistry of evermicose

Evermicose, an hydrolysis product of everninomicin B and D, has been shown to be 3-C-methyl-2,6-dideoxy-D-arabinohexose, or D-3-epimycarose.

Structure of evertetrose and everninonitrose

The structure and absolute stereochemistry of evertetrose and everninonitrose, two degradation products of everninomicin “D”, have been established.

Synthesis of 20-dihydro-20-deoxy derivatives of 16-membered macrolide antibiotics

The use of bis(triphenylphosphine)copper(I) tetrahydroborate for selective reduction of aldehyde tosylhydrazones in the presence of other reducible and sensitive functions, as present in macrolide antibiotics, is described.

Chemical degradation of AR-5 antibiotics (mycinamicins): X-ray crystal structure analysis of the aglycone from AR-5#2

The structures and stereochemistry of AR-5 antibiotics (mycinamicins) by X-ray analysis are disclosed; a novel degradative procedure for the preparation of the aglycones of the above antibiotics is also described.

Mutasynthesis of 23-O-mycinosyl-12,13-desepoxy-12,13-didehydro-rosaramicin from tylosin

A hybrid structure of rosaramicin and mycinamicin has been mutasynthesised and found to be highly active against gram positive organisms.

Structure of everninomicin-2

The structure of everninomicin-2 (2) has been elucidated and a method of conversion of everninomicin D (1) into (2) is discussed.