Disaccharides Containing Sugar Analogues or with Anomalous Linking

Compounds described as sugar rods and with phytohemagglutinin cross-linking properties, e.g. compound 108, have been made by a Pd-induced coupling reaction of propargyl and p-iodophenyl a-D-mannoside tetraacetate, and p-diiodobenzene led to the linear product with two propargyl a-D-mannoside substituents on the benzene rings. °  

Various tripeptides (112) containing serine p-D-galactosides have been examined for base stability. Replacing H by Me at had no effect, but a similar change at R caused appreciable increase in the rate of p-elimination, suggesting that the carbonyl group labelled A acts as a base to remove the illustrated proton and induce p-elimination of the sugar.  

Hydrogen peroxide oxidation of palatinose [a-D-Glc-(l- 6)-D-Fru] or trehalulose [a-D-Glc-(l- l)-D-Fru] affords carboxymethyl a-D-glucopyrano-side in about 40% yield. Various reactions of this product, e.g. its conversion to the bicyclic lactone involving 0-2 on treatment under acetylating conditions, were described.  

Physical studies on glycosides have included the X-ray diffraction analysis of methyl a-D-galactopyranosides and methyl p-D-glucopyranosides with fatty acid esters at C-6 which showed bilayer structures with zig-zag alkyl chains. The conformational behaviour of several non-ionisable lactose analogues have been examined by NMR and molecular mechanics methods, and the energy profile of methyl p-D-arabinofuranoside as a function of ring conformations has been determined by gas phase computations.  

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