Regine Blattner

Syntheses of the fungicide/insecticide allosamidin and a structural isomer

A synthesis of the naturally occurring inhibitor of chitin metabolism, allosamidin 1, involves, as the key step, condensation between the allosamizoline derivative 39, prepared following oxyamination of the cyclopentene 19, and the disaccharide glycosylating agent 54 which was synthesised from 2-acetamido-2-deoxy-D-glucose. The structural isomer 59 of allosamidin is also reported. Brief biological test results obtained using isomers 1 and 59 are recorded.

Intervention of catalytic amounts of water in the allylic rearrangements of glycal derivatives

Abstract It is confirmed that tri- O -acetyl- d -glucal with thiophenol in the presence of BF 3 ·OEt 2 as catalyst gives the allylically rearranged S -phenyl 4,6-di- O -acetyl-2,3-dideoxy-1-thio-α- and β- d - erythro -hex-2-enopyranosides as the main products, and now demonstrated that the presence of catalytic proportions of water diverts the reaction in favour of the isomeric S -phenyl 4,6-di- O -acetyl-2-deoxy-3-phenylthio-1-thio- d - arabino - and - d - ribo -hexopyranosides. It is proposed that these products are formed from an intermediate enal.

Crystalline pseudo-α-D-glucopyranose

Crystalline pseudo-α-D-glucopyranose, a compound of potential biochemical interest, has been obtained for the first time from a 6-deoxyhex-5-enopyranose derivative as starting material.

Direct synthesis of 6-oxabicyclo[3.2.1]octane derivatives from deoxyinososes

Abstract In the presence of bases, even those (for example, pyridine) normally used for acylation reactions, 2 l -(2,4, 5 3 )-2,3,4,-tribenzoyloxy-5-hydroxycyclohexanone (3) readily gives (2 l -(2, 4 3 )-2,3,4-tribenzoyloxycyclohex-5-enone or aromatic products. Under acid conditions, efficient O-acylation and tetrahydropyranylation can be effected. The main product (60% isolated) formed on treatment of 3 with diazomethane is (1R,2S,3R,4S,5S)-2,3,4-tribenzoyloxy-1-hydroxy-6-oxabicyclo [3.2.1]octane (15); small proportions of the epimeric spiro-epoxides and 1-acetyl-6-benzoyloxy-7-methoxy-1H-indazole are also formed. On photobromination, the acetate (17) of 15 undergoes substitution at C-7 and, from the product, C-formyl-deoxyinositol derivatives are produced.

Photo-bromination of carbohydrate derivatives. Part 2. Penta-O-acetyl-β-D-glucopyranose; the 5-bromo-derivative and products of further bromination

Photo -bromination of penta-O-acetyl-β-D-glucopyranose with N-bromosuccinimide in carbon tetrachloride causes specific replacement of H-5, and the 5-bromo-derivative can be isolated crystalline in high yield. By-products of the reaction contain monobromoacetyl and dibromoacetyl groups. When bromine was used as reagent the 5-substituted compound was again formed as initial product, but, ultimately, tetra-O-acetyl-α-D-glucopyranosyl bromide and dibromides with halogen substituents at C-1 and C-5, and with both bromine atoms at C-1, were also produced. A two-step route from glucose penta-acetate to 1,2,3,4-tetra-O-acetyl-6-deoxy-β-D-xylo-hex-5-enose is defined. Since the C-5 epimer of the penta-acetate affords the same products, it is proposed that the initial bromination proceeds by way of a discrete radical at the tertiary site.

Unsaturated carbohydrates. Part 28. Observations on the conversion of 6-deoxyhex-5-enopyranosyl compounds into 2-deoxyinosose derivatives

Mercury-containing intermediates have been isolated from the reaction of 6-deoxyhex-5-enopyranosyl compounds with mercury(II) salts in aqueous acetone. They react to give 2-deoxyinosose derivatives on further exposure to the conditions of their formation or, after isolation, by treatment with hydrogen sulphide. Mercury(II) acetate is more efficient than the previously used mercury(II) chloride for this carbohydrate-into-deoxyinosose conversion.

Effects of iron, copper, and chromate ions on the oxidative degradation of cellulose model compounds

Abstract Iron(II) and iron(III) ions promote the degradation of the cellulose model 1,5-anhydrocellobiitol by oxygen or hydrogen peroxide; copper and chromate ions have marked and different effects on the iron catalysis. With starch, iron promotes the hydrogen peroxide-induced reaction and copper and chromate ions further enhance the reaction rate. The tensile strength of paper board is reduced by the action of hydrogen peroxide and iron(II) salts, and mixtures of copper, chromate, and arsenate salts (CCA, a timber preservative) also promote degradation in the presence or absence of iron ions. The oxidation of 1,5-anhydrocellobiitol by oxygen in the presence of iron ions is strongly inhibited by CCA and by cetyltrimethylammonium chloride, and is accelerated by phenols and related compounds.

Unsaturated carbohydrates. Part 22. Alkenes from 5-bromohexopyranose derivatives

Base-catalysed elimination of hydrogen bromide from 5-bromo-β-D-glucopyranose penta-acetate and penta-benzoate gives predominantly the endocyclic products, whereas treatment with zinc–acetic acid affords a means of obtaining the exocyclic 6-deoxy-5-enose esters. All eight alkenes obtainable from these two bromo-compounds are reported together with their 1H and 13C n.m.r. spectra. Unsaturated compounds derived from penta-O-benzoyl-5-bromo-α-D-glucopyranose and acetylated 5-bromouronates are also reported. The conformations of all the alkenes are discussed and, in one case, the influences of the anomeric and allylic effects can be compared.

New approach to aminoglycoside antibiotics

Photobromination of peracylated hexopyranoses and treatment of the resultant 5-bromo-derivatives with zinc and acetic acid afforded 6-deoxy-5-enose esters which, with mercury(II) salts in aqueous media, gave 2-deoxyinosose triesters; applied to β-D-maltose octa-acetate, these procedures afforded an α-glucosylated inosose derivative which on further α-glycosylation gave a ‘pseudotrisac-charide’ related to those upon which aminoglycoside antibiotics are based.

Chain extensions from C-1 and C-5 of D-xylopyranose derivatives

Free radicals produced successively at C-5 and C-1 from corresponding D-xylopyranose-based bromides add to acrylonitrile and methyl acrylate to give products with β-propionitrile or β-propionate substituents at these positions; some steric control can be achieved in the reactions, and the 4,8-anhydroundecanose derivative (13) is produced with good selectivity.