Tetra Tetritol

An analogous scheme was revealed in the ammonolysis of 1,3,4,5-tetra-O-benzoyl-jS-D-fructopyranose and 1,3,4,5,6-penta-O-acetyl-keto-D-fructose,37 with formation of the imidazole derivatives 37, 38, 40, 41, and 4(5)-(D-arabino-tetritol-l-yl)imidazole (42), which were identified by paper chromatography. 

Base-catalyzed de-O-acetylation and deesterification of the 3-(tetra-0-acetyl - d - arabino - tetritol -1 - yl) - 4 - ethoxycarbonyl - 2,5 - dimethyl - 2-nitropyr -role 1 took place with concomitant y-lactone ring formation to provide the furo[3,4-c]pyrrol-l-yl acyclo C-nucleoside 2 [85AQ(C)49] (Scheme 1). 

Cylocondensation of tetra-O-acetyl-a/de/jydo-L-arabinose (143) with l-cysteine gave the thiazol-2-yl C-nucleoside 144 (76LA450). Acetylation of the latter gave the 7-(tetra-6>-acetyl-D-flrafo/no-tetritol-l-yl)thiazolo[3,4-cjoxazole 145 (94M189) (Scheme 44). 

The thiazole ring of the 5-(D-arahfno-tetritol-l-yl)-imidazo[2,l-6]thiazol-ium olate 160 was assembled onto the imidazole ring of 4-(tetra-0-acetyl-D-flrabino-tetritol-l-yl)imidazoline-2-thione (156) by reaction with 2-bromophenylacetic acid (91MI7) (Scheme 47). 

Methyl 1,2.3,4-tetra-O-acetyl- -D-galactopyranuronate Methyl 1,2.3,5-tetra-O-acetyl- -D-galactofuranuronate l-(p-Methoxyphenyl)-3-methyl-4-(D-arafcino-tetritol-l-yl)imi-dazolidine-2-thione... 

The number of five-membered heterocycles with four hetero atoms is limited to those with nitrogen atoms. Thus, the tetrazole acyclonucleo-sides were formed from sugars N,N -diphenylformazanes by the action of AT-bromosuccinimide or lead tetraacetate [133,134]. The synthesis of the tetra-O-benzoyl-D-lyxononitrile and its conversion to (o-lyxo-tetritol-l-yl)-tetrazole derivatives upon reaction with sodium azide was reported [133, 134]. A pseudo C-nucleoside including a tetrazole ring was achieved by conversion of 3- 0-benzyl- 1,2-O-isopropylidene-D-ribo-pentodialdehydo-1,4-furanose to the respective nitrile and then reaction with sodiiun azide [86]. 

Preparative Utility. Because of the ready availability of both enantiomers of arabinose, the reactions of the derived Cj dienophiles were evaluated in particular detail for potential preparative utility, with emphasis on the ability to separate by crystallization the major isomer from the reaction. Thus dienophile 6 reacted to give, by direct isolation, a 40% yield of pure, crystalline methyl (5Sf 6S)-6 endo-(1,2,3,4 tetra"Q"acetvl"D-arabino-tetritol-1-yl)bicyclo[2.2.l]hept-2-eno-5-sxo-carboxylate (22), mp 103.5—104.5 , [cr]n +73 , and likewise the L enantiomer of 6 gave methyl (5R,6E)-6-enfl2-(1,2,3,4-tetra-O-acetyl-L-arabino-tetritol-l-vl)bicyclo[2.2.11heDt-2-eno-5-exo-carboxylate (23). 

A very high degree of asymmetric induction was evident in the thermal reaction of the D-arabinose-derived cis-dienophile 20 with cyclopentadiene, and the crystalline adduct isolated in 95% yield was identified as methyl (5R,6S)-6-endo-(1,2,3,4-tetra-O-acetvl-D-arabino-tetritol-l-yl)bicyclo[2,2.1]hept-2-eno-5-endp-carboxylate (31), mp 103 by NMR spectroscopy and also by X-ray crystallography. Use of the same sequence starting from L-arabinose gave the enantiomer (32) of 31. 

The synthesis of tetra-O-benzoyl-D-lyxononitrile and its conversion to a (D-(yxo-tetritol-1-... 

The synthesis of 5-(tetra-0-acetyl-L-amZ>/ u-tetritol-l-yl)tetrazole, e/c., by reaction of acetylated aldononitriles with ammonium azide has been noted in Chapter 10. Related pentitol-l-yl heterocyclic compounds have been prepared... 

Gas-Liquid Chromatography.—Phthalic esters - which are extensively used as plasticizers in the formulation of plastics used to make containers for solvents, etc. - have been found as contaminants during the analysis of polysaccharides by gas chromatography of the alditol acetate derivatives for example, dibutyl phthalate behaves as a tetritol tetra-acetate on g.l.c. and di(2-ethylhexyl) phthalate has a retention time close to that for xylitol penta-acetate. The contamination by phthalic esters can be minimized by distilling all solvents used in the analytical steps or by using smaller volumes of potentially contaminated solvents. 

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