Higher-carbon sugars

Flgure10.23 Sialyl Lewis -related selectin inhibitorandfluorogenicscreening compound for transketolase prepared using enzymatic aldolization, and multienzymatic oxidation-aldolization strategy for the synthesis of bicyclic higher carbon sugars. 

Such aldolase-catalyzed bidirectional chain elongation ( tandem aldolization) of simple, readily available dialdehydes has been developed into an efficient method for the generation of higher carbon sugars (e.g. (87)/(89)) by simple one-pot operations (Figure 10.32) [126,156]. The choice offuranoid (87) or pyranoid (89) nature of the products can be determined by a suitable hydroxyl substitution pattern in a corresponding cycloolefinic precursor (86) versus (88)). The overall specific substitution... 

C. S. Hudson, The Fischer Cyanohydrin Synthesis and the Configurations of Higher-carbon Sugars and... 

Sugar allyltins (mentioned already in 2.2.3.) were used for the preparation of higher carbon sugars. This may be illustrated by reaction of the furano-side 99 with di-O-isopropylidene-D-arabinose performed under high pressure, which provided compound 100 (Fig. 33).43,48... 

Another approach to higher carbon sugars is based on the Wittig-type condensation between two properly activated sugar sub-units. The... 

Fig. 34 Approach to higher carbon sugars via the Wittig-type reaction Unusual rearrangement of the enone induced by triflate leaving group. 

C. Casiraghi and G. Rassu, Aspects of modem higher carbon sugar synthesis, in Studies in Natural Product Chemistry, Vol. 11, A.-ur Rahman, ed., Elsevier, Amsterdam, 1992, p. 429. J. S. Brimacombe, Higher carbon sugars, in Studies in Natural Product Chemistry, Vol. 4, part C, A.-ur Rahman, ed., Elsevier, Amsterdam, 1989, p. 157. 

See also J. S. Brimacombe, R. Hanna, A. K. M. S. Kabir, F. Bennett, and I. D. Taylor, Higher-carbon sugars. Part 1. The synthesis of some octose sugars via the osmylation of unsaturated precursors, J. Chem. Soc. Perkin Trans. 1, p. 815 (1986). 

O. Achmatowicz, An approach to the synthesis of higher-carbon sugars, in Organic Synthesis, Today and Tomorrow, B. M. Trost and C. R. Hutchinson, eds., Pergamon Press, Oxford, 1981, p. 307. 

For the total synthesis of aminodeoxy sugars from nonsugar precursors, it is logical to turn to amino acids as primary sources of chiral templates. The challenge is to find innovative and stereocontrolled methods of chain extension reactions that lead to higher-carbon aminodeoxy sugars. 

How, M. J., Brimacombe, J. S., and Stacey, M., The Pneumococcal Polysaccharides, 19, 303-357 Hudson, C. S., Apiose and the Glycosides of the Parsley Plant, 4, 57-74 Hudson, C. S., The Fischer Cyanohydrin Synthesis and the Configurations of Higher-carbon Sugars and Alcohols,... 

Carbon tetrafluoride is formed by passing gaseous fluorine over finely divided carbon (Norit).1 Sugar charcoal especially, and some wood charcoals, give large amounts of higher carbon fluorides and are to be avoided if the lower fluorides are desired. Norit seems to be the best when large yields of carbon tetrafluoride are desired. 

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