Duy-Phong Pham-Huu

Novel syntheses of densely functionalized indolizines, di- and tetrahydroindolizines from 2-formyl-1,4-dihydropyridine systems based on cascade process

Abstract Several indolizines, di- and tetrahydroindolizines have been synthesized successfully in a one-pot procedure, in two or three steps from 2-formyl-1,4-dihydropyridine derivatives and malonitrile in 57–87% yield. The general mechanism leading to these azacyclic compounds, involving 2-dicyanovinyl-1,4-dihydropyridines, is discussed.

Full acetals of β -d-glycopyranosylnitromethanes and a 1,2-dideoxy-1-nitroalk-1-enitol derived from common hexoses

Abstract Kinetically controlled O-isopropylidenation of common 2,6-anhydro-1-deoxy-1-nitroalditols (β- d -glycopyranosylnitromethanes) derived from d -glucose, d -galactose, and d -mannose with 2-methoxypropene in 1,2-dimethoxyethane catalyzed with 4-toluenesulfonic acid afforded high yields of 2,3;4,6-di-O-isopropylidene acetals. With d -mannose, the bisacetal was also obtained in quantitative yield by reaction with 2,2-dimethoxypropane. Mono-O-benzylidenation of the starting compounds with benzaldehyde dimethyl acetal followed by O-isopropylidenation led to 4,6-O-benzylidene-2,3-O-isopropylidene acetals having better solubilities in non-polar solvents than the di-O-isopropylidene acetals. Di-O-benzylidenation of β- d -mannopyranosylnitromethane gave both (endo-2,3):4,6- and (exo-2,3):4,6-di-O-benzylidene acetals. Transacetalation of 1-deoxy-1-nitro- d -mannitol with 2,2-dimethoxypropane followed by 2-O-acetylation and β-elimination of the acetoxy group afforded (E)-1,2-dideoxy-2,4:5,6-di-O-isopropylidene-1-nitro- d -arabino-hex-1 -enitol.

The first synthesis of a nitromethylene-linked C-(1→2)-disaccharide

Abstract The Michael addition of the 2,3:4,6-di- O -isopropylidene-β- d -mannopyranosyl-nitromethane nucleophile to 1,2-dideoxy-3,4:5,6-di- O -isopropylidene-1-nitro- d - arabino -hex-1-enitol affords a dinitro adduct that can be regioselectively reduced on the primary nitromethyl group to the oxime of the corresponding nitromethylene-linked C -(1→2)-disaccharide.

Behaviour of the Primary Nitro Group Under Denitration Conditions

ABSTRACT Treatment of per-O-acetylated or acetalated glycosylnitromethanes derived from the common hexoses and pentoses with tributyltin hydride and a catalytic amount of a radical initiator [1,1′-azobis(cyclohexanecarbonitrile)] in refluxing benzene easily afforded the corresponding glycosylmethanal oximes in 84-97% yields. Per-O-acetylated C-β-glycopyranosylmethanal oximes were employed for synthesis of versatile C-β-glycopyranosyl cyanides of the β-D-gluco, β-D-manno, β-D-galacto, β-D-xylo, and β-L-rhamno configurations.

A Simple and Expeditious Synthesisof Substituted 3-Aminoindolizines

Summary. Treatment of easily available 2-formyl-1,4-dihydropyridines with 3-oxo-3-phenylpropanenitrile offers a simple and efficient one-pot method for the preparation of substituted 3-aminoindolizines.Zusammenfassung. Die Umsetzung der einfach zugänglichen 2-Formyl-1,4-dihydropyridine mit 3-Oxo-3-phenylpropannitrilen stellt eine einfache und effiziente Eintopfmethode zur Darstellung substituierter 3-Aminoindolizine dar.

Conversions of Nitroalkyl to Carbonyl Groups in Carbohydrates

Since the development of the Sowden methodology in the middle of the twentieth century, several other efficient and complementary methods for the transformation of sugar nitromethyl groups to aldehyde functionalities in their free, hemiacetal, or otherwise derivatized forms have been developed. Hydrogen peroxide oxidation as well as ozonolysis of 1-deoxyalditol-1-nitronates in aqueous solution provide free aldoses, thus presenting alternatives to the well-known Nef reaction. When applied to 2,5- or 2,6-anhydro-1-deoxy-1-nitroalditols, also known also as glycosylnitromethanes, the Nef reaction fails, and the hydrogen peroxide oxidation overoxidizes the expected products to 2,5- or 2,6-anhydroaldonic acids. On the other hand, the ozonolysis of such compounds under pH-controlled conditions results in up to 85% of the interesting glycosylformaldehydes. The Nef reaction carried out in anhydrous low alcohols, however, has revealed a new conversion of glycosylnitromethanes to glycosylmethanal dialkyl acetals, even more interesting C-glycoside synthons. A similar acid-catalyzed methanolysis of 1-deoxyalditol-1-nitronates leads to methyl furanosides. Finally, a treatment of per-O-substituted glycosylnitromethanes with tributyltin hydride in boiling benzene causes their radical reduction under a nearly quantitative formation of glycosylmethanal oximes.