Kurt Hobert

Moenomycin A: A structural revision and new structure-activity reactions

Abstract A detailed FAB MS analysis combined with NMR and chemical results requires the structure of moenomycin A to be revised from 1a to 1b. New bio-chemical results seem to support the assumption that in the region F-G-H of lb the structural requirements for antibiotic activity are rather strict.

Moenomycin A: further structural studies and preparation of simple derivatives

Abstract Preparation of the moenomycin A derivatives 2 – 5 is reported. Structure 1 proposed for moenomycin A is confirmed by 13 C NMR and fast atom bombardment mass spectrometry data. Compounds 2 and 3 are antibiotically active whereas methyl derivatives 4 and 5 lack activity.

Structures of some moenomycin antibiotics-inhibitors of peptidoglycan biosynthesis

Abstract Isolation, structural assignment, and antibiotic efficiency of the new moenomycin antibiotics C3 (1b) and C4 (1c) is decribed. The previously published structure of pholipomycin (1d) is modified.

Synthesis of (+)-strigol, (+)-4′-epi-strigol, and their enanthiomers

Abstract A short synthesis of the title compounds amenable to large-scale preparation is reported. Key feature is a simple resolution step.

Moenomycin A - Structure-activity relations synthesis of the D-galacturonamide analogue of the smallest antibiotically active degradation product of moenomycin A

Abstract Compound 10c which is the galacturonamide analogue of 2, the smallest degradation product of moenomycin A (1) with full antibiotic activity, has been synthesized. 10c is devoid of antibiotic activity.

Botrydial synthetic studies. Asymmetric synthesis of quaternary carbon centres

Abstract The synthesis of optically active 4 has been accomplished by asymmetric formation of cyclic β-keto esters fully substituted at the α-carbon followed by chemoselective reduction of the ester group. Of the asymmetric reactions examined the Koga procedure proved to be the most selective.

The first moenomycin antibiotic without the methyl-branched uronic acid constituent.- Unexpected structure activity relations

Abstract Isolation and structure elucidation of a new moenomycin antibiotic (C1, 1e) that lacks the branching methyl group in the 4-position of unit F are reported. The smallest antibiotically active degradation product of 1e is the trisaccharide derivative 3. This observation is in contrast to structure activity relations in the moenomycin A series where it was found that disaccharide 4a is fully active.

On the stereochemistry of the BF3-catalyzed rearrangement of (+)-isophorone oxide

Abstract The title reaction proceeds with partial or extensive racemization depending on the solvent used.

The first enzymatic degradation products of the antibiotic moenomycin A.

Abstract Moenomycin A was degraded by enzymatic cleavage of the bond between the moenuronic acid moiety and the phosphate group. The phosphoric acid monoester 4a could be dephosphorylated further to yield 3a . Compound 3a was used to confirm the previous configurational assignment at C-2 of the glycerate part of moenomycin A and to prepare ent - 4a . 4a and ent - 4a are antibiotically inactive.

Synthesis and transglycosylase-inhibiting properties of a disaccharide analogue of moenomycin A lacking substitution at C-4 of unit F

Abstract A disaccharide analogue ( A4 = 13c ) of moenomycin A lacking the OH group in the 4-position of the uronic acid moiety has been synthesized using the Saito deoxygenation reaction as key step. 13c does not inhibit the transglycosylase (PBP 1b), a key enzyme in the biosynthesis of bacterial peptidoglycan. The result demonstrates the importance of this OH group for the binding of disaccharide moenomycin analogues to the enzyme.