Abstract
Adenosylhopane is a putative precursor of the widespread bacterial C35 biohopanoids. A concise and flexible hemisynthesis of adenosylhopane has been developed including as key steps a cross metathesis between two olefins containing either the hopane moiety or a protected adenosine derivative and a subsequent diimide reduction of the resulting olefin. Reduction by deuteriated diimide allowed deuterium labelling. This synthetic protocol represents a versatile tool to access to deuteriated composite bacterial hopanoids required for biosynthetic studies. Deuteriated adenosylhopane was thus converted into bacteriohopanetetrol by a crude cell-free system from Methylobacterium organophilum in the presence of NADPH, showing for the first time the precursor to product relationship between these two bacterial metabolites.
Highlights
Adenosylhopane is a putative precursor of the widespread bacterial C35 biohopanoids
The commonly occurring configuration of adenosylhopane was determined by circular dichroism and highfield NMR spectroscopy.1a Trace amounts of (22S)-adenosylhopane as the minor isomer was reported from Rhodopseudomonas acidophila.1b Chemical conversion of adenosylhopane 2 into bacteriohopanetetrol 5 permitted the determination of the stereochemistry of all asymmetric centres of the side-chain of bacteriohopanetetrol as 22R, 32R, 33R and 34S.1b Later the synthesis of the eight side chain diastereomers of bacteriohopanetetrol confirmed that the absolute configuration of the C5 unit was identical to that of a D-ribitol linked via its C-5 carbon aUniversité de Strasbourg/CNRS, Institut Le Bel, 4 rue Blaise Pascal, F 67070 Strasbourg, Cedex, France
This paper describes an efficient hemisynthesis of adenosylhopane including the possibility of deuterium labelling as well as the conversion of deuterium labelled adenosylhopane into bacteriohopanetetrol by a crude cell-free system form Methylobacterium organophilum, which represents the first
Summary
Adenosylhopane is a putative precursor of the widespread bacterial C35 biohopanoids. A concise and flexible hemisynthesis of adenosylhopane has been developed including as key steps a cross metathesis between two olefins containing either the hopane moiety or a protected adenosine derivative and a subsequent diimide reduction of the resulting olefin. Reduction by deuteriated diimide allowed deuterium labelling This synthetic protocol represents a versatile tool to access to deuteriated composite bacterial hopanoids required for biosynthetic studies. Deuteriated adenosylhopane was converted into bacteriohopanetetrol by a crude cell-free system from Methylobacterium organophilum in the presence of NADPH, showing for the first time the precursor to product relationship between these two bacterial metabolites. Two distinct methods are available to produce complex hopanoids: fermentation or chemical synthesis. Fermentation is only appropriate for a few major compounds as many complex hopanoids are produced by bacteria in only trace amounts. Identified genes in Methylobacterium extorquens, Rhodopseudomonas palustris and Streptomyces coelicolor: (i) hpnH/orf[15]; (ii) hpnG/orf[14]; hpnO/orf18.10–13 synthesis, in contrast, allows an access to a broad range of naturally occurring hopanoids in sufficient amounts. Extensive work resulted in suitable syntheses of ribosylhopane, bacteriohopanetetrol and several other related structures.[6,14,15,16,17] Some synthetic strategies are quite successful with excellent stereochemistry control and good overall yields
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