Sugar dialdehydes cyclization

An unusual observation was made on nitroethane cyclization of the dialdehydes (37 a) and (37 b), obtainable from a- and p-methyl D-gluco-pyranoside (36), respectively, by periodate oxidation. In distinct contrast to the course of the nitromethane cycUzations of these and a range of other sugar dialdehydes D, the products that result, i.e. (43), have undergone epimerization at C-5 as compared to (39). thus raising the number of isomers to be expected to 16. 

Scheme 4. Richardson s application of the Fischer nitromethane cyclization to the sugar dialdehyde derived from the periodate cleavage of levoglucosan (1960).

Glycosides of 3-deoxy-3-nitroaldoses are readily available by the cyclization of sugar dialdehydes with nitromethane. Introduced in 1958 by Baer and Fischer,48 the method has been widely employed, and some aspects have been reviewed.49,50 The term sugar dialdehydes refers to products of glycol cleavage of glycosides.51 The formation, structure, conformation, and reaction of such dialdehydes have been discussed in detail in previous Chapters of these Volumes.52-54 The compounds exist in aqueous and alcoholic solutions as solvated, cyclic forms that are internal hemialdals or hemiacetals.54 However, under the conditions of the nitromethane cyclization, mobile equilibria are rapidly shifted from such cyclic products toward carbonyl species, and it is, therefore, permissible and customary in... 

In view of the great facility with which base-catalyzed alkoxylations of nitro-olefinic sugars tend to occur, it might be suspected that side reactions involving the formation of methylated derivatives might accompany nitromethane cyclizations of sugar dialdehydes in methanolic medium. There is as yet no evidence for this, but special... 

The dialdehydes, such as VI and XI, produced by periodate oxidation of sugar glycosides or polymers, very probably do not exist in the aldehydo form,212-214 but in a hydrated212 and cyclized structure.213 214... 

Aldol-type cyclization of dialdehydes with nitroalkanes is a valuatde syndietic loute to amino sugars, amino cyclitols and nucleosides of amino sugars. Recently, die cyclization of die di- and tetra- de-hydes derived from sucrose (15) with nitroalkanes has appeared. It is notewordiy that the oxidadve cleavage of sucrose with LTA affords the dialdehyde selectively (Scheme 8). ... 

Ribonucleosides (47) or synthetic analogs (48) containing a )3-d-glucopyranosyl, instead of the /J-D-ribofuranosyl, residue are amenable to periodate cleavage of their sugar moieties, to give nucleoside dialdehydes (49). Nitromethane cyclization of such dialdehydes proceeds well, and affords stereoisomeric mixtures of (3-deoxy-3-nitro-/3-D-hexopyranosyl)pyrimidines or (3-deoxy-3-nitro-/3-D-hexopy-ranosyl)purines (50). 

Several 4-deoxy-4-nitro ketose derivatives have been synthesized. Three crystalline 2,7-anhydro-4-deoxy-4-nitro-/3-D-heptulopyranoses arose by nitromethane cyclization92 of the dialdehyde (74) produced by periodate oxidation of sedoheptulosan (73), and were assigned93 the D-alio (75), D-gulo (76), and D-altro (77) configurations by nuclear magnetic resonance spectroscopy of the corresponding, peracetylated amino sugars. When the cyclization of 74 was performed in methan-olic medium, a solid mixture of stereoisomeric nitronates was obtained in almost quantitative yield, and it could be partially separated into the individual nitronates, which furnished 75 and 76. The isomer 77... 

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