Lyxose pyridine

Pentapropionyl-D-galactononitrile has been prepared in 52 % yield by Gim6nez from the oxime and pyridine-acetic anhydride. Degradation with ammonia-silver oxide produced D-lyxose diacetamide in 30% yield. 

Pentabenzoyl-D-galactononitrile was obtained in 98% yield from the oxime and pyridine-benzoyl chloride 5-benzoyl-D-lyxose in 22% yield was obtained by degradation with ethanolic ammonia. 

The selective tritylation of pentoses has been studied, and providing that the reaction is conducted at below 25 C and with only one equivalent of trityl chloride, the 5-0-tritylate is the major product. However, even under these conditions lyxose afforded substantial amounts of diethers, and the 5-monoether was isolated in only 32% yield. The monotritylation of D-xylose has been studied in detail at 50 °C in the presence of either pyridine or AgOAc-HMPT, and four of the monotrityl ethers were isolated as tetra-O-acetyl derivatives. The ratio of 1-, 3-, 4-, and 5-substitution was 36 0 25 100 (in pyridine) and 0 49 57 100 (AgOAc-HMPT). The products were also prepared unequivocally by the tritylation of the appropriate D-xylose tetra-acetate. The selective tritylation of methyl a- and j3-L-rhamnosides has also been studied the a-anomer giving the 3-, 4-, and 2-trityl ethers in 57, 3, and 1% yields respectively. The j3-anomer afforded the 3- and 4-trityl ethers in 34 and 17% yields respectively. Pyridinium perchlorate has been used for the selective de-O-tritylation of otherwise peracetylated methyl gluco- and manno-pyranosides. ... 

Heating an aqueous solution of L-ascorbic acid containing pyridine and boric acid causes decarboxylation and the formation of lyxose and xylose, and reaction of the acid with L-tryptophan at pH 7 for extended periods led to several products including compounds (18) and (19), which were mutagenic to a bacterium. ... 

An investigation of the structures of the D-pentose phenylhydrazones in water, methanol, and pyridine by chemical, spectroscopic, and chiroptical methods has indicated that the acyclic form is adopted in these solvents. A related study has shown that D-glucose phenylhydrazone also adopts the acyclic form in DMSO, whereas solutions of the corresponding 4-nitro- and 2,4-dinitro-phenylhydrazones in DMSO contain only 40 and 10%, respectively, of the acyclic form. An n.m.r. study of 2,5-anhydro-D-lyxose and -xylose 4-nitrophenylhydrazones is mentioned in Chapter 20. 

Further examples of rearrangements involving cyclic sulphonium ions have been reported. Thus 2,3,5-tri-0-methyl-4-0-toluene-/>-sulphonyl-D-ribose diethyl dithioacetal (184) and dibenzyl dithioacetal (185) gave 4- S -ethyl-2,3,5-tri-0-methyl-4-thio-L-lyxose (186) and benzyl 2,3,5-tri-0-methyl-l,4-dithio-a-L-lyxo-furanoside (187) (Scheme 46) when heated either in aqueous pyridine or with sodium iodide in acetone similar rearrangements to the 4-thiofuranosides were observed with 2,3,5-tri-0-methyl-4-0-toluene-p-sulphonyl-D-xylose and -lyxose... 

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