João R. de Freitas Filho

Microwave-induced synthesis of 2,3-unsaturated O-glycosides under solvent-free conditions

Abstract Microwave irradiation of a mixture of tri- O -acetyl- d -glucal 1 and an appropriate alcohol 2a – f , in the presence of Montmorillonite K-10 as a catalyst, provided unsaturated glycosides 3a – f in much shorter time and in yields comparable with conventional heating.

Synthesis and hypolipidemic activity of N-phthalimidomethyl tetra-O-acyl-α-d-mannopyranosides

Abstract A facile synthesis of anomerically pure phthalimidomethyl 2,3,4,6-tetra- O -acetyl- and phthalimidomethyl 2,3-di- O -acetyl-4,6-di- O -benzoyl-α- d -mannopyranosides ( 6 and 9b ) starting from N -hydroxymethylphthalimide and tri- O -acetyl- d -glucal is described. Compounds 3 , 6 , 8 , 9a and 9b have been tested for their hypolipidemic activity in mice. All these compound showed significant reduction of plasma cholesterol and triglyceride levels. Compound 9b has been found to possess the highest activity.

D‐Glucose, a Fascinating Biomolecule: History, Properties, Production and Application

Os carboidratos sao as biomoleculas mais abundantes na Terra e anualmente sao produzidos aproximadamente 200 bilhoes de toneladas desses compostos pelas plantas superiores e algas.Dentre os inumeros compostos classificados como carboidratos, a D-glicose e de longe o monossacarideo mais abundante. AD-glicose e um dos poucos carboidratos de baixa massa molecular, economicamente atrativo, produzido em larga escala e propenso a modificacoes estruturais para a producao de novos compostos.A D-glicose e utilizada nos mais variados setores industriais, tais como: no alimenticio, farmaceutico, cosmetico, quimico dentre outros. Diante disto, e justificavel o aumento anual da demanda de D-glicose, na qual ela pode ser obtida por distintos processos industriais, como a hidrolise acida e a hidrolise enzimatica.Em funcao da relevância da D-glicose, este artigo apresenta uma revisao sobre a historia, as propriedades, a producao e biossintese deste composto.

Recent Advances in C-Glycoside Chemistry: Application, Synthesis and Reactions

A sintese de C-glicosideos, analogos de acucar em que o oxigenio glicosidico e substituido por um atomo de carbono e de particular interesse devido a sua utilidade como intermediarios chave para a montagem de moleculas e produtos naturais biologicamente ativos. Apesar da sua quimica desafiadora, devido a sua versatilidade, os C-glicosideos desempenham um papel fundamental no desenvolvimento da quimica de novos materiais e moleculas bioativas. Nesta revisao, apresentamos varias metodologias sinteticas, proposta mecanicista e aplicacao de C-glicosideos 2,3-insaturados nos ultimos vinte ano

Synthesis of Cyclohexyl 6-O-Trityl-alpha-D-Threo-Hexopyranosid-4-ulo-(2,3:3',4')-2-Pyrazoline

Reaction of tri-O-acetyl-D-glucal (1) with cyclohexanol (2) using Ferriers method provided the unsaturated cyclohexyl glucoside 3, which furnished the title compound 12 in a sequence involving hydrolysis, selective tritylation of oxygen at C-6, allylic oxidation with MnO2 and 1,3-dipolar cycloaddition with diazomethane. Starting from 6, product 17 was obtained in four steps. Semi-empirical molecular orbital calculations (AM1) were carried out for compound 12 which gave an idea about its stable conformation, and also supported the existence of the anomeric effect. Attempts to open the pyrazoline ring in 12 and 17 failed. Partial negative charge at C-3 was responsible for the lack of reactivity of 12 towards reduction of C=N bond.