The Methyl 3-Nitro-3-Deoxy- And 3-Amino-3-Deoxy-Arabinopyranosides

Abstract

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

Conformational Preference and Configurational Equilibria of the Methyl 3-Deoxy-3-nitro-pentopyranosides and their Nitronates

“…One puzzlement of long standing has been the seemingly exceptional behavior of methyl 3-deoxy-3-aci-nitro-P-D-erythro-pentopyranoside sodium (2), the main product inthe nitromethane cyclization of 1, which on acidification gave both 3-epimers, with methyl 3-deoxy-3-nitro-p-D-'Part XIX of a series on the reactions of nitro sugars. ribbpyranoside (6) unexpectedly preponderating P-D-arabinopyranoside 9; in other words, opposite configurations were engendered at C-3 in these two nitronates (3). The 3-epimers of 8 and 9, i.e.…”

“…The nitromethane cyclization of L'-methoxydiglycolaldehyde (1) and its D' enantiomer (I*)' (1)(2)(3), and many further applications of this reaction which have recently been reviewed (4), have provided facile access to a large body of nitrogenous carbohydrates. In the course of these investigations a stereochemical rule has emerged that concerns the liberation of 3-deoxy-3-nitroaldopyranosides (and analogous 4-deoxy-4-nitro-ketopyranose derivatives) from their aci salts, in which process a new center of asymmetry is created.…”

A New Approach to 3′-Amino-3′-deoxynucleosides. Synthesis of 9-(3-Amino-3-deoxy-α-L-ribofuranosyl)adenine

“…Complete separation from remnant 10 could not be effected, but a sample enriched in this by-product was hydrogenated and hydrolyzed with hydrochloric acid for inspection by paper chromatography. The major, ninhydrin-positive spot had the same mobility as an authentic sample of 3-amino-3-deoxy-L-arabinose hydrochloride (25), and a minor spot corresponded to the L-rib0 isomer. Assignment of the a-L-arabinofuranosyl structure to the by-product must remain tentative but would be in line with previous results (1 1).…”