Other Trideoxy Sugars

Disregarding nonoxygen functional groups (amino, dimethylamino, and so on) only the 2,3,6-trideoxyhexoses were isolated from natural products. However, some of the isomeric trideoxyhexoses were chemically synthesized. Thus, the methyl a-glycosides of 3,4,6 - tr i de o xy - d - erj f/ ro - he x o p y r a n o s e, 3,4,6-tri-deoxy-D-t/zreo-hexopyranose and 2,4,6-trideoxy-D-eryt/iro-hexopyranose were synthesized from methyl 4,6-dideoxy-a-D-xy/o-hexopyranoside via selective sub- 

Starting from L-rhamnono-1,4- or 1,5-lactone, via p-elimination reactions, 3,5,6-trideoxy-a-DL-t/zra -hexose276 or 3,4,6-trideoxy-DL-t/zreo-hexose has been obtained.277 

Kirschning, A. F. W. Bechthold, and J. Rohr, Chemical and biochemical aspects of de-oxysugars and deoxysugar oligosaccharides, Top. Curr. Chem., 188 (1997) 1-83 H. W. Liu and J. S. Thorson, Pathways and mechanisms in the biogenesis of novel deoxysugars by bacteria, Anna. Rev. Microbiol., 48 (1994) 223-256. 

Kirschning, M. Jesberger, and K. U. Schoning, Concepts for the total synthesis of deoxy sugars, Synthesis (2001) 507-540. 

de Lederkremer and C. Gallo, Natural occurring monosaccharides Properties and synthesis, Adv. Carbohydr. Chem., 59 (2004) 9-67. 

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In all cases, the sugar residues are attached to the 7-hydroxy group and this is the point of interest to carbohydrate chemistry. Until present, only the 3-amino-2,3,6-trideoxy sugars daunosamine (62) and rhodosamine (63) were found to be a-glycosi-dically linked to this position. The other saccharides 2-deoxy-L-fucose (64), L-cineru-... 

Ethoxy-3,4-dihydro-6-methyl-2ff-pyran (179) has been used78 as the substrate for the synthesis of methyl 2,3,6-trideoxy-a-DL-enjthro-hex-2-enopyranoside (180). The synthesis consisted in hydroboration of the double bond, followed by oxidation, bromination at C-2, and elimination of HBr, to give 180. This compound was, in turn, converted into methyl DL-mycaminoside,7K DL-oleandroside,79 and other sugar glycosides (see Section III,2). 

Other examples of the presence of this sugar are the LPSs from Rhizobium loti, which contain mainly 6-deoxytalose with small amounts of the 2-O-methyl derivative.181 The O-specific polysaccharide chain of Proteus penneri LPS also contains 6-deoxy-L-talose, together with another rarely occurring sugar, 2,3-diacetamido-2,3,6-trideoxy-L-mannose.182... 

Modifications of amino-sugars covered in other chapters include 6-deoxygenatlon of 2-amino-2-deoxy-D-galactose and -glucose, and synthesis of methyl 2-acetamido-2,3,6-trideoxy-B-L-lyxo-hexo-pyranoside (Chapter 12), syntheses of six 2-amino-2-deoxyheptonlc acids (Chapter 16) and of pseudonucleosides (Chapter 20), and the tritiation of aminoglycoside antibiotics (Chapter 19). 

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