Idopyranose preparation

Carba-y5-DL-idopyranose (77) was prepared from (readily accessible) (l,2,4/3)-5-(hydroxymethyl)-5-cyclohexene-l,2,3,4-tetrol (75) by hydrogenation over a platinum catalyst, acetylation of the product, and 0-deacetylation. 

Much information concerning such a ring enlargement has been accumulated. For historical reasons, the preparation of L-idopyranose derivatives will be discussed first. 

When either of the two methods in the previous Subsection is employed in order to introduce a phosphino (or phosphinyl) group at C-5 of 5-deoxy-D-xyZo-hexofuranoses, only 5-deoxy-5-phosphino- (or -5-phos-phinyl)- L-idopyranoses are produced for instance, 50 — 60 (and 64) — 63 (and 65), and 73 — 78 — 85 — 88 — 90. Therefore, in order to prepare hexopyranoses of the D-gluco type having phosphorus in the hemiacetal ring, an alternative approach had to be devised. 

Hanaya, T, Fujii, Y, Ikejiri, S, Yamamoto, H, A new route for preparation of 5-deoxy-5-hydroxyphosphinyl-D-gluco- and L-idopyranose derivatives. Heterocycles, 50, 323-332, 1999. 

While the aforementioned methodologies constitute the most useful and general synthetic procedures for the preparation of 1,6-anhydropyranoses, a number of alternative routes have been described [27]. As mentioned previously, solutions of a number of sugars in aqueous acid at equilibrium contain considerable amounts of 1,6-anhydro sugars. A simple synthesis of tri-0-acetyl-l,6-anhydro-/J-L-idopyranose has been reported by Stoffyn and Jeanloz that utilizes the acid-catalyzed dehydration of L-idose to form the anhydro ring [28]. 

Oxirans.- The acid-catalyzed hydrolysis of 5,6-anhydro-l,2-0-iso-propylidene-B-L-ldofuranose has been re-examined, because the conditions reported previously for the preparation of L-ldose were found not to give a pure product conditions for optimum production of L-idose, 1,2-0 -lsopropylidene-B-L-ldofuranose, or 1,6-anhydro-L-idopyranose were found.The 2,5 3, -dlanhydride (5) has been synthesized from 1,2-0-cyclohexylldene-a-D-xylofuranose via the dltosylate (6) (Scheme 1). Sulphonyloxy groups at C-3 in acetals such as (7) are reported to be readily displaced with the... 

Methyl 2-acetamido-5,6-anhydro-2-deoxy-0 -L-idofuranoside (33) has been synthesized from 2-acetamido-2-deoxy-D-glucose and has been employed in the preparation of 2-acetamido-5-amino-2,5-dideoxy-D-glucopyranose as the sulphur dioxide adduct (34) (Scheme 7). Similarly the corresponding idopyranose was prepared in an analogous manner. ... 

A racemic synthesis of 3,4-dideoxy-2- -methyl-4-phenylphosphinyl-D. L-alvcero-tetrafuranose has been reported as has the preparation of the four epimers of 5-deoxy-3-Q-methyl-5-C-[(R)-and (S)-phenylphosphinothioyl]-Q- and j8-D-xylopyranoses (see SPR Vol 21, p 167). The preparation of 5-deoxy-5-[(RS)-ethylphosphlnyl]-a,/8-L-idopyranoses has been described,and 1,2,4,6-tetra-Q-acetyl-5-deoxy-3-Q-methyl-5-[(RS)-phenylphosphinyl and methyl phosphinoyl] a,j9-L-idopyranoses have been prepared. ... 

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