Having a Phosphinediyl or Phosphonyl Group in the Pyranose Ring

Monosaccharides Having a Phosphinediyl or Phosphonyl Group in the Pyranose Ring 

In order to synthesize monosaccharides having phosphorus in the hemiacetal ring, it is obvious that two fundamental problems have to be solved (I) how to introduce a suitable phosphine group, having the desired orientation, into an appropriate position on the carbon skeleton of the precursor, and (2) how to accomplish efficient ring-closure in order to yield the desired monosaccharide possessing a ring-phosphorus atom. 

Because of the absence of a chiral center at C-5, such pentopyranoses as 7 were judged to be the most amenable to preparation and study. In 

Reduction of 10 with lithium aluminum hydride (LAH) in ether furnished19 an intermediate, presumably the phosphine derivative 11, which was treated with acid to effect ring enlargement, giving the 5-phosphino-D-xylopyranose derivative 14. This compound was immediately converted by air oxidation19 into the stable crystalline compounds, 5-deoxy-3-0-methyl-5-C-(phosphinyl)-D-xylopyranose (15) and the 5-C-(hydroxyphosphinyl) derivative 16 in overall yields of 15 and 3.5%, respectively, from 10. Compound 16 was obtained in 90% yield from 15 by oxidation with bromine.19 No mutarotation was observed19 for compounds 15 and 16 in water during 48 h. 

An unambiguous, structural assignment was made23 by converting the anomeric mixture 16 into the tri-0-acetyl-5-C-(methoxyphosphinyl) derivatives 17 by treatment with diazomethane and then with acetic anhydride-pyridine after chromatographic separation, structures 19-22 [all in the 4Ct(D) conformation] were established for each product by analysis ofthe 400-MHz, -n.m.r. and high-resolution mass spectra (see Section 11,5). The overall yields of these products from 10 were 19 (6.5), 20 (2.7), 21 (4.9), and 22 (3.3%). 

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