Wittig reaction hydroxyl directed

When the Wittig reaction was run directly on (6), a substantial amount of the isomer (10) was also obtained. This product is considered to arise through (9), formed by an intramolecular Meerwein-Ponndorf reaction involving the hindered carbonyl group and the free hydroxyl group. 

Analogues 249 (X = H, OH) of UDP-GlcNAc have been prepared as potential inhibitors of chitin synthetases. The synthetic route involved a C-allyl derivative of GlcNAc, which was elaborated by ozonolysis, Wittig reaction and coupling with the nucleoside, followed by hydrogenation or hydroxylation as appropriate. The corresponding amides were also prepared from 5 -amino-5 -deoxyuridine. Lipophilic amino acid methyl esters and methylamides have been coupled to 0-5 of AZT by carbamate links. The products showed anti-HIV activity, but this was not due to carbamate hydrolysis or to direct inhibition of reverse transcriptase, and the mechanism of action may be one not previously observed with nucleoside antivirals. ... 

The idea was that the lactone 227 could come from 228 by the sequence (i) stereo- and regioselective a-hydroxylation 229, (ii) Wittig style reaction on the ketone to add the extra two carbon atoms 230, (iii) stereoselective conjugate reduction of the double bond with the OH group directing the reagent to the bottom face of the alkene, and (iv) lactonisation. 

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