The nitromethane cyclization of L'-methoxy-diglycolic aldehyde was shown t o furnish methyl 3-nitro-3-deoxy-a-L-arabinopyranoside and methyl 3-nitro-3-deoxy-p-D-arabinopyranoside as coproducts of the previously obtained p-D-ribo isomer. As expected, the enantiomorphic dialdehyde, D'-methoxy-diglycolic aldehyde, afforded the corresponding WD-and P-L-arabino derivatives in addition to the 6-L-ribo isomer. Catalytic hydrogenation of the four new nitroglycosides gave the corresponding aminoglycoside hydrochlorides. The 3-amino-3-deoxy-D-and L-arabinose hydrochlorides were obtained from their glycosides by hydrolysis and crystallized as mutarotating p-forms.The spontaneous epimerization, in aqueous solution, of aci-nitropentoside sodium salts was investigated.In the cyclization (I), with nitromethane and sodium methoxide, of L'-methoxydiglycolic aldehyde (I) a methyl aci-nitrodeoxy pentoside sodium salt had been isolated in crystalline condition in a yield of about 40%. This salt had been shown to possess formula I1 and must therefore be denoted as methylRlanifold experiences gathered subsequently in similar nitromethane condensations and recorded in papers of this series have borne out the hardly surprising fact that this type of reaction does not proceed in a stereospecific way, although a notable stereoselectivity is always observed. I t was of interest, therefore, to investigate whether, and to which extent, stereoisomers of I1 were formed in the reaction which produced the latter as the apparent main product. The three possible stereoisomers of I1 which might arise from the dialdehyde I are the corresponding a-L-threo (111), P-D-threo (IV), and a-L-erythro (V) 3-deoxypentose derivatives. The present study was-intended, furthermore, to uncover the cause of the previously~observed mutarotation of 11; i.e. to verify in the pentose series that glycoside nitronates in solution are liable to undergo spontaneous epimerizations, as has been found to be the case with nitronates derived from hexosides (2, 3).We are now able to demonstrate that when dialdehyde I is cyclized with nitromethane, the a-L-threo and P-D-threo forms of methyl 3-aci-nitro-3-deoxypentopyranoside sodium (I11 and IV, respectively) indeed occur in the reaction mixture as minor components beside the chief product, p-D-erythro salt 11. Although the salts I11 and IV could not be isolated as such, their presence was indicated by the isolation of two new, free nitroglycosides that arose upon deionization of the mixture. Thus, methyl 3-nitro-3-deoxy-a-L-arabinopyranoside (VI), originating from 111, and methyl 3-nitro-3-deoxy-P-D-arabinopyranoside (VII), arising from IV, were obtained in yields of approximately 5% each.These crystalline nitroglycosides were hydrogenated to furnish the corresponding aminoglycosides, which crystallized as hydrochlorides: methyl 3-amino-3-deoxy-a-L-arabinopyranoside hydrochloride (VIII) and methyl 3-amino-3-deoxy-0-D-arabinopyranoside
The dialdehyde I1 that arises from a partial lead tetraacetate cleavage of sucrose has been cyclized with nitromethane to give a stereoisomeric mixture of nitro disaccharides IV via their sodium nitronates 111. Upon catalytic hydrogenation a single amino disaccharide, a-D-glucopyranosyl 4-amino-4-deoxy-P-~-gluco-heptulopyra1loside hydrochloride (V), was isolated. Various derivatives of the nitrogenous heptulose components of IV and V were prepared by methanolysis and hydrolysis. The configuration of V was established by a degradation of its N-acetyIated hydrolysis product, 4-acetarnido-4-deoxy-a-D-gluco-heptulose (VII), which gave 2-arnino-2-deoxy-D-arabinose hydrochloride, and by reduction of VII, which gave the two epimeric acetanlido heptitols XI I1 and XIV.
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