An improved synthesis of 6β-hydroxy-5β-pregnane-3,20-dione

6β-Hydroxy-5β-pregnane-3,20-dione, formerly prepared by a hydroboration method, has been obtained in greatly improved yield by a simpler irradiation-hydrogenation procedure.     

3-Carbamoyl-α-picolinic acid production by imidase-catalyzed regioselective hydrolysis of 2,3-pyridinedicarboximide in a water-organic solvent, two-phase system

3-Carbamoyl-α-picolinic acid, a versatile building block for the synthesis of agrochemicals and pharmaceuticals, was prepared by imidase-catalyzed regiospecific hydrolysis of 2,3-pyridinedicarboximide with intact Arthrobacter ureafaciens O-86 cells. Reactions were carried out in a water-organic solvent, two-phase system containing cyclohexanone at low pH to avoid spontaneous random hydrolysis. Under the optimized conditions, with the periodic addition of 2,3-pyridinedicarboximide (in total, 40 mM), the 3-carbamoyl-α-picolinic acid yield reached 36.6 mM in the water phase, with a molar conversion yield of 91.5% and a regioisomeric purity of 94.5%, in 2 h at pH 5.5. Received: 7 February 2000 / Received revision: 13 March 2000 / Accepted: 3 April 2000     

An improved synthesis of α,β-unsaturated nitrones relevant to the stephacidins and analogs thereof

A new method is reported for the synthesis of the α,β-unsaturated nitrone moiety characteristic of the stephacidin/avrainvillamide family of bioactive prenylated indole alkaloids. Application to the synthesis of stephacidin analogs and a potential biological probe are showcased.     

An efficient synthesis of γ-hydroxy-α,β-unsaturated aldehydic esters of 2-lysophosphatidylcholine

The diverse biological activities of ??-hydroxyalkenal phospholipids and their involvement in disease are the subject of intense study. Phospholipid aldehydes, such as the 4-hydroxy-7-oxohept-5-enoic acid ester of 2-lyso-phosphatidylcholine (HOHA-PC), the 5-hydroxy-8-oxo-6-octenoic acid ester of 2-lyso-PC (HOOA-PC), and the 9-hydroxy-12-oxododec-10-enoic acid ester of 2-lyso-PC (HODA-PC), are generated by oxidative cleavage of polyunsaturated fatty acyl phospholipids. To facilitate investigations of their chemistry and biology, we now report efficient total synthesis of HOOA, HODA, and HOHA phospholipids. Because the target ??-hydroxyalkenals readily decompose through oxidation of the aldehyde group to a carboxylic acid or through cyclization to furans, these synthesis generate the sensitive functional array of the target phospholipids under mild conditions from acetal derivatives that are suitable for long-term storage.     

Photochemical addition of 2-propanol and of acetone to methyl 5-deoxy-2,3-O-isopropylidene-β-d-erythro-pent-4-enofuranoside

High-capacity adsorbents for lectins, including Lotus tetragonolobusl-fucose-binding protein, were readily prepared by conjugation of monosaccharides with commercially available, epoxy-activated Sepharose. Purified, radioiodinated lectins were bound to cells of the mosquito Aedes aegyptii and of human KB tumour. Relative to human KB cells, mosquito cells bound less of lectins specific for the sugars (l-fucose and d-galactose) that are terminal residues in many mammalian glycoproteins, whereas the number of binding sites of lectins specific for core-region sugars (d-mannose and 2-acetamido-2-deoxy-d-glucose) were similar. Neuraminidase, which greatly enhanced binding of peanut agglutinin or soybean agglutinin to human KB cells, had negligible effects on binding of these lectins to mosquito cells. The comparative structures of surface oligosaccharides of mosquito and KB cells are discussed in relation to the lectin-binding studies.     

Addition of hydrazoic acid to methyl 6-O-benzoyl-2,3-dideoxy-α-D-glycero-hex-2-enopyranosid-4-ulose

The title compound 4 reacted with hydrazoic acid to give exclusively an adduct having the threo configuration, whose structure was established by reduction to the lyxo derivatives 8 and 10. The reaction of 4 with hydrogen peroxide afforded the epoxide 12, the lyxo structure of which was deduced by conversion into the alcohol 13. Tributylborane also reacted with the enone 4, giving the adduct 15, whose configuration was tentatively assigned to be threo.     

Synthesis and some reactions of methyl 4,6-O-benzylidene-2,3-dideoxy-2-phenylazo-β-d-erythro-hex-2-enopyranoside

Methyl 4,6-O-benzylidene-2,3-dideoxy-2-phenylazo-β-d-erythro-hex-2-enopyranoside has been synthesised, and its addition reactions with methoxide, azide, hydride, and deuteride ions have been studied. Comment is made on the stereochemistry of addition reactions of 2- and 3-phenylazo derivatives of methyl 4,6-O-benzylidene-2,3-dideoxy-d-hex-2-enopyranosides.     

A kinetic study on the reductive opening of the diphenylmethylene acetal in methyl 2,3-O-diphenylmethylene-α-L-rhamnopyranoside

Reductive opening of the diphenylmethyl acetal in methyl 2,3-O-diphenylmethylene-α-l-rhamnopyranoside has been investigated by kinetic studies, and the results have been compared to those recently obtained by quantum chemical calculations. In contrast to the previous theoretical calculations which related only to the presumably rate limiting step of the reductive opening, the reaction system LiAlH(4), AlCl(3), and the title compound consists of at least four simultaneous reactions. Nevertheless, reasonable agreement can be found between the activation Gibbs free energy obtained from kinetic measurements and the theoretically calculated ones in spite of the experimental errors and the approximate nature of theoretical calculations.