Synthesis and Monosaccharide Chemistry of KDO

In the original work of Ghalambor and Heath,29,31 attempts at opti- 

In the experience of the present author, minor deviations from this procedure may result in decreased yields. Oxalacetic acid of high quality is essential, and this should be verified by a melting-point determination prior to use. Decarboxylation of oxalacetate has been reported111 to occur rapidly at pH 7, and it should be kept to a minimum by maintaining the pH as close to 10 as possible when dissolving the oxalacetic acid. A modification of the Comforth reaction is the co-balt(II)-ion-catalyzed condensation of D-erythrose 4-phosphate with oxalacetate to give 3-deoxyheptulosonic acid 7-phosphate112 (as a mixture of the arabino and ribo isomers). Other procedures for the preparation of KDO will be discussed in subsections 3 and 4 of this Section. 

The enol lactone 88 is also an intermediate in a Wittig synthesis98 of KDO (compare Section IV,4). Hershberger and Binkley100 utilized cer- 

Kochetkov and coworkers78,121 synthesized KDO by a Wittig route, starting from 2,3,4,5-tetra-O-acety 1-aZdehydo-D-arabinose (91), as follows. The reaction of 91 with (fert-butoxyoxalyl)methylenetriphen- 

Esterification of 104 with diazomethane gives 70 in quantitative yield.80 The low yield previously obtained29,31 may have been due to impure starting-material. Compound 70 is crystalline,29,31 and may be used for the preparation of the ketopyranosyl chloride 112 by the method that Kuhn and coworkers109 reported for the synthesis of the analogous halide of NeuAc. In this procedure, compound 70 is dissolved in acetyl chloride, and the solution is cooled to —70°, saturated with hydrogen chloride gas, and allowed to warm to room temperature in a sealed container. The preparation of 112 in this way was first reported by Bhattachaijee and coworkers,101 and, shortly thereafter, by Unger and coworkers.128 The Canadian authors synthesized the 

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