- Racemic and enantioselective total synthesis of heliespirones A & C
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An account of the total synthesis of (±)-, (+)-heliespirone A and (±)-, (-)-heliespirone C is presented. In the first-generation total synthesis, we found rac-24a could be easily transformed to rac-heliespirones A & C in a biomimic way. Taking the disappointing diastereoselectivity of prenylation from 3 to 4, the nonselective dihydroxylation from 4 to 5 and the lenthy route in strategy A into account, we designed a different synthetic plan targeting a highly enantioselective, concise and protective-group free synthesis of heliespirones A & C. The palladium-catalyzed Michael addition and Sharpless AD played the key roles in the formation of optical lactone V, which could be easily transformed to compound I through two additional steps and the succedent operations were the same as those in the first-generation total synthesis. Our synthetic efforts indicated the bio-generation of heliespirones A & C from 24a should be a real process in nature.
- Huang, Chong,Zhang, Wenhan,Liu, Bo
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- Compositions based on direct dyestuffs containing a 2,5-dihydroxyphenylcarboxylic acid or a salt thereof
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A composition suitable for dyeing keratin fibres, especially human hair, is provided comprising a direct dyestuff and, as a levelling agent, a 2,5-dihydroxyphenylcarboxylic acid or a salt thereof.
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