A-D-lyxose

SCHEME 2. Richardson s unsuccessful attempted oxidative degradation of a D-lyxose diethylsulfonyl dithioacetal possessing a fused acetal (1959). 

Figure 2. Hydroxyl PMR signals for a-D-tagatopyranose (upper left) and a-D-mannoheptulopyranose (lower left) in methyl sulfoxide-d6. 13C NMR spectra of a,fi-D-tagatose (3) and a-D-lyxose in water and of a,/ -D-tagatose in methyl sulfoxide-(ppm relative to downfield 13CS2)-...

Lemieux and Brice have measured the rate of exchange (in chloroform) of a large number of 1,2-trans sugar acetates with stannic trichloride acetate labeled with C. Their results are given in Table XVII. The low reactivities of the acetates of 8-D-ribose, a-D-lyxose, 8-D-allose, and a-D-mannose (rela-... 

In summary, these peracylated derivatives lead to conformational equilibria, except in the case where the issue is particularly obvious a-D-xylo, Ci -D-arabino, C4 configurations). The free pentoses in aqueous solution still remain to be seen. The diaxial interactions are stronger than with the acetates and the anomeric effect is weaker. Out of the eight D-pentose configurations, four of them (jS-D-arabinose, a-D-lyxose, a-D-ribose, and jS-D-ribose) lead to a conformational equilibrium. 

Shikimic acid, and its phosphonic acid analogue, have been made from a D-lyxose derivative by sequences involving intramolecular Wadsworth-Emmons reactions, in a manner very reminiscent of that employed earlier by Fleet and Shing (Vol. 17, p. 165 Vol. 18, p. 172),1 and the previously-reported enone (21), made from di-O-isopropylidene-a-D-glucofuranose (Vol. 21, p. 180), has been converted into the known intermediate (22) in a prior synthesis of paniculide B.l ... 

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