Imidazole sugar derivatives

A sugar derivative related to the purine nucleosides, namely methyl 5-(adenin-l-yl)-5-deoxy-2,3-0-isopropylidene-j8-D-ribofurano-side, is formed by the reaction of methyl 5-amino-5-deoxy-2,3-0-iso-propylidene-jS-D-ribofuranoside with l-benzyl-5-cyano-4[(ethoxy-methylene)amino]imidazole, followed by removal of the benzyl group. On fusion, this compound rearranges to methyl 5-deoxy-2,3-0-isopropylidene-5-[(purin-6-yl)amino]-/8-D-ribofuranoside, which can also be obtained from the reaction of methyl 5-amino-5-deoxy-2,3-0-isopropylidene-/8-D-ribofuranoside with 6-chloro-9-(tetrahydropyran-2-yl)purine. In the same manner, methyl 5-amino-5-deoxy-2,3-di-0-p-tolylsulfonyl-/3-D-ribofuranoside reacts with 6-chloro-9-(tetrahydro-pyran-2-yl)purine to give methyl 5-deoxy-5-[9-(tetrahydropyran-2-yl)-purin-6-yl]amino-2,3-di-0-p-tolylsulfonyl-j8-D-ribofuranoside. With liquid ammonia, 5 -0-p-tolylsulfonyladenosine gives 5 -amino-5 -deoxyadenosine. On heating in p-dioxane, ring closure to 3,5 -an-hydroadenosine is observed. ... 

Imidazole-l-sulfonate Displacements at the C-3 and C-4 Positions of Sugar Derivatives. Displacement reactions of tosylates at the C-3 position of a-D-glucopyrano-side derivatives proceed with difficulty because of a nonbonded 1,3-diaxial interaction between the aglycone and the approaching nucleophile [32], as well as complications arising from neighboring group participation [90]. 

Synthesis of the imidazol-4-yl acyclo C-nucleoside 403 has been described (93MI2 95TL3165) by condensation of the aldehydo-sugar derivative 51 with 4-lithioimidazole to give the hemiacetal C-nucleoside 451, which formed 403 upon treatment with an acid (Scheme 111),... 

In the reaction of ammonia with l,3,4,5-tetra-0-benzoyl-/3-n-fructopyranose, a significant proportion of benzoic acid was formed, indicating that the ammonolysis of the sugar ester occurred to a certain extent through acyloxy-group rupture. As neither the formation of imidazole nor of pyrazine derivatives (see Section VI,3, p. 124) re-... 

As previously indicated (see pp. 88-91), formation of heterocyclic compounds, mainly pyrazines, was found only in the ammonolysis of some aldose nicotinates33 35 and acetates and benzoates of ketoses.39 37 For ketose esters, whose behavior differed from that of the aldose esters, the formation of imidazole derivatives was also observed these heterocyclic compounds also result from the direct action of ammonia upon the corresponding free sugars, but the presence of the esterifying acyl groups evidently increases their ease of formation and raises their yields. 

Formation of imidazole derivatives in the reaction of ammonia with free sugars has been reviewed.39... 

Considerable work was done to induce chirality via chiral auxiliaries. Reac tions with aromatic a-ketoesters like phenylglyoxylates 21 and electron-rich al kenes like dioxoles 22 and furan 23 were particularly efficient (Scheme 6). Yield up to 99% and diastereoselectivities higher than 96% have been observed whet 8-phenylmenthol 21a or 2-r-butylcyclohexanol 21b were used as chiral auxiliarie [14-18]. It should be noted that only the exoisomers 24 and 25 were obtained from the reaction of dioxoles 22. Furthermore, the reaction with furan 23 wa regioselective. 24 were suitable intermediates in the synthesis of rare carbohydrate derivatives like branched chain sugars [16], Other heterocyclic compounds liki oxazole 28 [19] and imidazole 29 [20] derivatives as well as acyclic alkenes 3fl 31, and 32 [14,15,21,22] were used as olefinic partners. Numerous cyclohexane derived alcohols [18,21-24] and carbohydrate derivatives [25] were used as chiri... 

Photochemical Balz-Schiemann reaction of diazonium fluoroborates continues to be the method of choice to prepare fluoro substituted imidazoles. Thus, 4(5)-fluoroimidazole 1565 is prepared from 4(5)-nitroimidazole 1559 in moderate yield by conversion of the nitro group to the diazonium salt followed by irradiation in aqueous tetrafluoroboric acid. Sugar-fluoroimidazole derivatives 1566 and 1567 were prepared using an iV-silyl derivative of 1565 (Scheme 404). 

Figure 4. TMS derivatives of several sugars as resolved on the 7Z phenyl-7X-cyanopropyl-polymethyl slloxane liquid phase DB-1701. Split Injection (In acetonltrlle/TMS imidazole 1 1) on a 30 m x 0.25 mm column coated with a bonded 0.25 pm film. Hydrogen carrier at 40 cm/sec 180°C 2 min, and 5 /mln to 200. Components 1, D-arablnose ...

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