Approaches to higher-carbon sugars, based on the use of sugar-derived, stabilized Wittig reagents
✍ Scribed by Slawomir Jarosz; David Mootoo; Bert Fraser-Reid
- Publisher
- Elsevier Science
- Year
- 1986
- Tongue
- English
- Weight
- 868 KB
- Volume
- 147
- Category
- Article
- ISSN
- 0008-6215
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✦ Synopsis
l-( 1,2 : 3,4-Di-O-isopropylidene-cu-D-galactopyranuronyl)imidazole, obtained by treating the corresponding diacetal of cr-D-galactopyranuronic acid with l,lcarbonyldiimidazole, reacts with methylenetriphenylphosphorane to give (1,2:3,4di -0 -isopropylidene -(Y-D -galactopyranuronyl) -(triphenylphosphoranylidene)methane (3) as a crystalline, stable Wittig reagent. Compound 3 reacts with aldehydo sugars to provide cY,/3-unsaturated ketones, preponderantly as the E isomers. The a&unsaturated ketones react with lithium dimethyl cuprate to afford an -3: 1 mixture of the 1,Caddition products, and with methylmagnesium chloride to give a 12: 1 mixture of the tertiary allylic alcohols methyl 5-deoxy-5-C-[7-deoxy-1,2:3,4-di-0-isopropylidene-6-C-methyl-D(and L)-glycero-ar-o-galacto-heptos-7(E)-ylidenel-2,3-0-isopropylidene-P_D-ri-ribofuranoside, which undergoes an oxidative rearrangement when treated with pyridinium chlorochromate.