Xylose deuterated

However, it should be noted that the concept of carbohydrates as chiral synthons has always fascinated sugar chemists as the excellent 1972 review by Inch will attest 42). Thus in order to preserve historical perspective three antecedents for the use of sugars in asymmetric syntheses are noted in Scheme 1. First is Wolfrom s proof of the structure of (-t-)-alanine by synthesis from D-glucosamine 102). Second is the synthesis of the optically pure mandelic acid derivatives from 2,3-4,5-di-O-isopropylidene-fl/tfeAy o-D-arabinose (1) by Bonner (9), and third is Lemieux s synthesis of ethanol-l-d from diacetone glucose (6 a, Scheme 2) via the deuterated xylose (2) (57). 

In a seminal contribution, Bock and co-workers conducted mechanistic studies on soluble as well as immobilised xylose isomerase from Streptomyces murinus sp. (Sweetzyme Q from NOVO) employing NMR-spectrometric methods. These studies confirmed the lack of deuterium exchange with solvent molecules of D-glucose and D-fructose regiospecifically C-deuterated at C-1 and C-2 [31]. It is noteworthy that they found the (IS)-diastereomer of D-(l- H)fruc-tose (29) was formed with perfect selectivity by isomerisation of D-(l- H)glu-cose (28) and so was the corresponding (IR)-epimer (31) when D-(2- H)glu-cose (30) was employed as the substrate (Scheme 6). 

There have been many reports of syntheses of deoxy nucleosides by standard sugar-base condensation reactions. These include 5 -deoxy-ribo nucleosides and 5 -mono- or 5",5-di-deuterated analogues, as well as derivatives of 5-deoxy-D-xylose and 5-deoxy-D-glucose, 5-alkylated thymidine derivatives, 2 -deoxy-6-methyl-5-azacytidine and its a-anomer, the thymidine analogue 4-(2-deoxy-B-D-erythro-pento-furanosyl)-6-methyl-l,2,4-triazine 3(HH)-one-1-oxide, 6-aza-3-deaza analogues of 2 -deoxy-cytidine and 2 -deoxyuridine,3 -deoxycytidine from a 3-deoxy-ribofuranose obtained from a fermentation broth producing the 3 -deoxy nucleoside antibiotic, cordycepin, 4-deoxy-DL-threo-pentopyranosyl pyrimidine nucleosides, and 5 -C-methyluridines derived from 6-deoxy-D-allose and 6-deoxy-D-talose. A range... 

The Kishi-Nozaki reaction [71] is the key step in the preparation of methyl C-isomaltoside (Scheme 40) [72]. Coupling of vinyl iodide 150 with the xylose derivative 151, readily available in six steps from L-xylose, afforded the corresponding allylic alcohol with a diastereomeric ratio of 15 1 in favor of 152. Finally, selective hydrogenation of the double bond and oxidation of the primary alcohol led to the C-disaccharide 153, which could be converted to its methyl glycoside 21. A useful dideuterated derivative of C-isomaltoside 154 for solution conformation studies was also accessible from this synthetic approach via the m-deuteration of the alkene intermediate 152 with Pt on AI2O3 and D2. 

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