Determinaçao da configuraçao de acetal de ácido pirúvico em polissacarídeo de molusco Pomacea lineata (Spix, 1827)

Orientador: José Hazencleve Duarte Tese (Doutorado) -Universidade Federal do Paraná. Curso de Pós-Graduaçao em Bioquímica Resumo: As galactanas acidas isoladas de glandulas de albumen de Pomaoea lineata foram purificadas por precipitacao fracionada, usando-se cetavlon (brometo de hexadeciltrimetila_ monia) em pH 7 e em pH 8,5, na presenca de tampao borato. Am bos os polissacarideos isolados (F.A e F.B, respectivamente), contem unidades de 8-P-galactopiranose, grupo acetil e acetal de acido piruvico 0-(1-carboxietilideno), numa relacao molar de 23:5:1. A analise de metilacao demonstrou que o grupo d-(1-carboxietilideno) foi ligado, numa proporcao de 3% a 0-3 e 0-4 das unidades terminais nao redutoras de F.AeF.B. Estes polimeros sao altamente ramificados, tendo 38% de unida des terminais nao redutoras de Z?-galactopiranose, unidades 3,6-di-d-substituidas (41%) e de alguns segmentos lineares de unidades mono-substituidas em > ga'Laetopyranosi 1 units. Smith degradation studies i$fs?3!Olving 3 successive steps demonstrated that the nuclei of the polysaccharides are relatively rich in 3-0-substituted units. The periodate-resistant residues of deacetylated F.A and F.B, which contain acetals, are either principally single-unit side-chains or are part of longer side-chains not oxidized by periodate. In the course of the successive degradations, selective oxidation took place in relatively longer side-chains whose components were terminal and 6-0-substituted. The polymers of Marisa oornuarietis differ from those of V P. lineata, at least in that they have terminal units of L-fucopyranose. \ In order to determine the absolute configuration of the pyruvic acid acetals of the P, lineata polysaccharide a number of 3,4-0-(1-carboxyethylidene)-derivatives of methyl g-P-galactopyranoside and methyl g-P-fucopyranoside were prepared, each of them in both configurational forms. Their carbon-13 and proton n.m.r. spectra contained. configurationally-dependent signals that were compared with equivalent signals in the spectra of the acidic galactan. In 13 terms of the ring size of the acetal, the C chemical shift of the signal corresponding to the non-protonated acetal carbons of the polysaccharide (6c 109.0) was in the region of 5-membered (6^ 107-109.5) rather than 6-membered rings (