MMPP. Therefore, formaldehydedimethylhydrazone behaves as a newneutral formyl anion and cyanide equivalent, introducing a functionalized carbon unit β to the nitro group of a nitroolefin. Good yields and high stereoselectivities were obtained in the addition of 1 to a nitroolefin group within sugar derivatives, and no epimerization was observed in the cleavage of the dimethylhydrazone group.
Diastereoselective Synthesis of Branched-Chain Cyanonitrosugar Derivatives by Michael Addition/MMPP Oxidation Using Formaldehyde SAMP- and RAMP-Hydrazones as New Chiral Cyanide Equivalents
The diastereoselective synthesis of sugar derived β-nitro nitriles through double asymmetric induction experiments involving Michael addition of formaldehyde SAMP- and RAMP-hydrazones [(S)-1 and (R)-1] to sugar nitroolefins 2 in excellent overall yields and high diastereoselective excesses is described. The absolute configuration of the RAMP-hydrazone 1,4-adduct 3c was determined by chemical correlation of its corresponding β-nitro nitrile 4c.
Regio- and stereoselective synthesis of 3- and 5-(C-glycosyl)-4-nitroisoxazolidines by nitrone–nitroalkene [3+2] cycloaddition reactions
作者:Pastora Borrachero、Francisca Cabrera、Mª Jesús Diánez、Mª Dolores Estrada、Manuel Gómez-Guillén、Amparo López-Castro、José Mª Moreno、José L. de Paz、Simeón Pérez-Garrido
DOI:10.1016/s0957-4166(98)00488-1
日期:1999.1
Cycloaddition reactions of nitrones, including sugar nitrones, with nitroalkenes, including sugar nitroolefins, led with complete regioselectivity and stereospecificity to 4,5-trans-4-nitroisoxazolidines in 51-78% global yields. The endo/exo stereoselectivity depends on the type of sugar derivative used. As expected, the best pi-diastereofacial selectivity was observed when both partners were sugar derivatives. Isomerisation of the first formed diastereomers by the action of silica gel was observed in some cases. Absolute configurations for two crystalline products were assigned by X-ray diffraction methods. (C) 1999 Elsevier Science Ltd. All rights reserved.
2-Glycosylchromene Derivatives
作者:Jean M. J. Tronchet、Sami Zerelli、Gérald Bernardinelli
DOI:10.1080/07328309908544000
日期:1999.1.1
Treated with salicylaldehyde or its 5-methoxy derivative, a series of blocked terminal (E)-nitroenoses undenwent a condensation reaction leading in fair to good yields to blocked 2-glycosyl-3-nitro-2H-chromene derivatives. Treated with cyanide, the nitro derivatives afforded 4-cyano-2-glycosyl-2H-chromenes via an addition-elimination reaction. These two types of chromenes bearing an electron-withdrawing group have been previously shown to have antiviral or cytotoxic properties related to their electrophilicity.
Influence of the structure of the sugar moiety on the cytotoxic and antiviral properties of sugar electrophiles.
Blocked sugars bearing a 2-nitrovinyl, 1-cyanovinyl, 3-nitrochromen-2-yl or 4-cyano-chromen-2-yl group have been prepared. Their cytotoxicity and chemotherapeutic properties depend on the structure of the sugar moiety. Some of these compounds active against Polyoma virus constitute leads for the development of new antiviral drugs.