David W. Hutchinson

Glucose is a precursor of 1-deoxynojirimycin and 1-deoxymannonojirimycin in Streptomyces subrutilus

Abstract Streptomyces subrutilus ATCC 27467, when grown on a glucose-containing soyabean medium, produces both 1-deoxymannonojirimycin (DMJ) and 1-deoxynojirimycin (DNJ) in its culture medium. When 1- or 2-[2H]-D-glucose is used, the deuterium label appears at C6 in both alkaloids and the labelling pattern suggests that the first step in the biosynthesis of both DNJ and DMJ is a glucose to fructose isomerisation. Studies with 5-2H]- and 6,6-2H2-D-glucose indicate that oxidation of the 6-position of the glucose/fructose occurs during the biosynthesis and that mannonojirimycin is the first aminosugar to be formed. Mannonojirimycin can then undergo dehydration and reduction to DMJ. Alternatively, epimerisation of mannonojirimycin can occur at C2 to give nojirimycin which is then dehydrated and reduced to DNJ.

The structure of dicoumarol and related compounds

Abstract From a study of nuclear magnetic resonance and infrared spectra, intramolecularly hydrogen-bonded structures are proposed for dicoumarols ( 9 ), 3-(α-acetonylbenzyl)-4-hydroxycoumarin (Warfarin) ( 13 ) and dimethones ( 8 ). A possible relationship between such hydrogen-bonded structures and the biological activities of ( 9 ) and ( 13 ) is suggested.

The enzymatic synthesis of antiviral agents

The majority of potential antiviral agents which are currently undergoing clinical trials are inhibitors of the replication of nucleic acids. The most common class of these inhibitors are nucleoside analogues and the elucidation of synthetic routes to these compounds has been of interest for many years as many are anticancer agents. One synthetic development has been the application of bio-transformations to nucleoside syntheses. This topic has been reviewed recently (Shirae et al., 1991) but this review is not widely available. In the present review, the application of biotechnology to the synthesis of antiviral agents including those which are not nucleoside analogues will be discussed. Enzymatic syntheses of nucleosides can be simpler and quicker than syntheses carried out by chemical methods. The most useful enzymes are those found in catabolic pathways. Nucleoside phosphorylases and N-deoxyribosyltransferases have both been widely used for nucleoside synthesis catalysing the transfer of sugar residues from a donor nucleoside to a heterocyclic base. Enzymatic methods have also been applied to the resolution of racemic mixtures and adenosine deaminase is a convenient catalyst for the hydrolysis of amino groups on purines and purine analogues. Regioselective deprotection of nucleoside esters has been achieved with lipases and these enzymes have also been applied to the synthesis of esters of sugar-like alkaloids. The latter have potential as inhibitors of the replication of HIV. Esterases have also been used in combined chemical and enzymatic syntheses of organophosphorus antiviral agents.

Metal chelators as potential antiviral agents

Metal-chelating compounds can inhibit virus-induced enzymes in infected cells by coordinating with metal ions at their active sites. Consideration of the coordinating properties of ligands can explain the antiviral activity of these compounds. The antiviral actions of a number of compounds (e.g., thiosemicarbazones, pyrophosphate analogues, beta-diketones, cyclic polyethers and flavanoids) are discussed in the light of their metal-chelating properties.

Michael addition reactions of ethenylidenebisphosphonates

Abstract Tetraethyl and tetraisopropyl ethenylidenebisphosphonates can undergo facile Michael-type addition reaction with nitrogen, phosphorus or sulphur nucleophiles (but not with oxygen or carbon nucleophiles) to give C-substituted methylene-bisphosphonates. In the case of sulphur nucleophiles, the products can be readily isolated and de-esterified to give the corresponding bisphosphonic acids, which are potential inhibitors of the replication of influenza virus A.

The biosynthesis of 1-deoxynojirimycin in Bacillus subtilis var niger

Abstract Bacillus subtilis var niger ATCC 9372 when grown on a glucose containing soyabean medium produces the amino-sugar 1-deoxynojirimycin (DNJ). The C2 epimer 1-deoxy-mannojirimycin (DMJ) present in Streptomyces subrutilus ATCC 27467 is absent. 13C and 2H labelling studies confirm that glucose is the precursor of DNJ. Randomisation of the 13C label from 1-[13C]-D-glucose and the incorporation of 1-[13C]-D,L-glyceraldehyde into DNJ also suggest that a minor part of the biosynthetic route involves cleavage of the glucose skeleton. Mannojirimycin (MJ) and nojirimycin (NJ) are postulated intermediates in the biosynthesis as a result of both enzyme assay and isotope labelling studies.

New approaches to the synthesis of antiviral nucleosides

There is a pressing, worldwide need for new antiviral agents. The chemical synthesis of novel nucleosides for chemotherapeutic screening usually involves multistage processes which can be time consuming. The application of enzymatic methods for the synthesis and modification of antiviral nucleosides shows great promise because of the simplicity and high specificity of enzymatic reactions.

Synthesis of alkylated methylene bisphosphonates via organothallium intermediates

Abstract Thallium(I) derivatives of esterified methylene bisphosphonates can be readily obtained by treating the latter with thallium(I) ethoxide under anhydrous conditions. Alkylation of the thallium(I) derivatives by a range of primary alkyl iodides takes place smoothly, and significantly higher yields are obtained than for the corresponding reactions with lithio or sodio derivatives.

Studies on pyruvate decarboxylase: acyloin formation from aliphatic, aromatic and heterocyclic aldehydes

Evidence is described that supports the view that the enzyme responsible for acyloin formation from aldehydes in the yeast Saccharomyces cerevisiae is pyruvate decarboxylase.

Poly(5-hydroxycytidylic acid)

Abstract In an improved method for the synthesis of 5-hydroxycytidine diphosphate (ho5CDP), CDP is treated with bromine in the presence of 2,4,6-collidine and the products of the reaction purified by ion exchange chromatography. Polymerisation of ho5CDP by polynucleotide phosphorylase (polyribonucleotide orthophosphate:nucleotidyl transferase, EC 2.7.7.8) is difficult and only takes place in the presence of large amounts of the enzyme and with a [Mg2+]:[substrate] ratio of 1:1. In contrast to poly(5-halogenocytidylic acids), poly(ho5C) appears to have little secondary structure in neutral or acid solution and does not appear to form a complex with poly(G), poly(I) or poly(A).