Anhydroaldonic Acids and Lactones

Some 0-tosyl-lactones (e.g. 20 and 21) have been cyclized to tetrahydrofuran derivatives (22 and 23 respectively) on boiling in dioxane-water and synthesis of 2-deoxy-4-ep/-neuraminic acid and 2,4-dideoxy-neuraminic acid have been recorded. Liposomes functionalized with neuraminic acid by way of a C- 

Reagents i, BusSnLi ii, BuLi, CIC02Me iii, NaHMDS, BrCH2C02Bu  

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The base-catalysed ring-contraction of 5-lactone 2-triflates to homochiral tetrahydrofurans (Vol. 26, p. 169) now has a complementary acid catalysed procedure, as exemplified by the conversion of 23 to 24, and of 25 to 26, on treatment with HQ in methanol at room temperature. Under these conditions, the triflate 27 gave the expected product, but with K2CO3 in MeOH the bicyclic oxetane 28 was obtained in 86% yield, a result rationalized by a mechanism involving initial P-elimination fiom 27. Cyclic sulfates can also be used to make anhydroaldonic acids, as... 

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