Lyxose synthesis

The synthesis of diol 56 from L-lyxose is reported. Compound 56 constitutes a subunit of the toxin erythroskyrine <96JCS(P1)1323>. 

A key reaction in the synthesis of the TIA alcohol 18 was the Suarez fragmentation (33) of the 2,3-O-isopropylidene-D-lyxose derivative 23 (34). Treatment of 23 with diiodobenzene diacetate (DIB) provided the 1,2-0-isopropylidene acetate 24 in 88% yield. Acetal exchange was effected by treatment of 24 with thiophenol and BF3.Et20 at -78 °C. Mild base hydrolysis of the product provided 18 in 90% yield from 24, and in 65% overall yield over the four one-pot operations for commercially available D-lyxose 22 (Scheme 3). 

The Wohl degradation214 of suitably acetylated aldononitriles was used for the synthesis of 5-deoxy-L-arabinose,216 5-deoxy-D-lyxose,2W and 5-deoxy-D-ribose.217 

Good diastereoselectivities were observed for the hetero Diels-Alder addition of homochiral 1,3-dienes with achiral acyl-nitroso dienophiles. An example is shown in Scheme 13.85 for the total synthesis of 4-amino-4,5-dideoxy-L-lyxose derivatives 300 and 301, potent inhibitors of a-L-fucosidase [160]. 

Walker et al. have described by tliis method a seven-step synthesis of 4-thio-2-deox-y-i3-eri f/7ro-pentosc (37) from 2-dcoxy-D-erir/ira-pentosc via dithioacetals 35 and 36, involving inversion at C-4 by Mitsunobu reaction and final cyclization of the dithioacetal, accompanied by further inversion at C-4. Secrist et al.- have synthesized 39 from the ribose derivative 38 using the same method. Similarly, Imbach et al. have prepared 1,4-dithio-D-ribofuranosides 39 from L-lyxose and from D-ribose,and 1,4-dithio-L-lyxofuranosides 40 from D-ribose. Mackenzie 

The details on the preparation of the glycone synthon 16 have been described in the earlier report on 3 (24). The key reactions in this synthesis is the Suarez radical fragmentation of the 1,2-O-isopropylidene furanose 17 to give the 1-O-acetyl-1,2-isopropylidene 18 (35), and acetal exchange of 18 to the phenylthio monothioacetal 16 (Scheme 2). Overall, 16 is easily obtained on multi-gram scale (ca. 20 g), in 60% yield, over five steps from commercially available D-lyxose. 

An optically pure cyclic analogue of aziridine-2-carboxylate ester was prepared from ribose via a Ph3P-promoted conversion of 3-azido-2-tosyl-D-xylofuranoside to its corresponding 2,3-aziridine (95) (Scheme 34) <93T90l>. The procedure is directly applicable to the synthesis of enantiomerically pure 2,3-aziridine carboxylate isomers from D-lyxose. 

Lipides, 238, 239, 241-243, 261 Lipidosis, 239, 242, 243 Lobry de Bruyn-Alberda van Ekenstein transformation, 63, 291 acid catalysis of, 79 aldolization in, 77 base catalysis of, 79-81 catalysis of, by metal ions, 81 dealdolization in, 77 dehydration reactions in, 73 enzyme-catalyzed, 66, 70 formation of reductones in, 79 of or-hydroxy aldehydes, 71 mechanism of, 84 of noncarbohydrate a-ketols, 71 non-enzymic, 66, 67, 83 in paper chromatography, 81 rearrangement of carbon chain, 79 scope of, 65 of steroids, 72 use of, for synthesis, 82 Lyxonic acid, 3-deoxy-D-, 300 Lyxose, D-, condensation of, with urea, 218 

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