Isoprene units derived from dimethylallyl diphosphate (DMAPP) are an important motif in many natural products including terpenoids, carotenoids, steroids, and natural rubber. Understanding the chemical characteristics of DMAPP is an important topic in natural products chemistry, organic chemistry, and biochemistry. We have developed a direct bioinspired indole prenylation reaction using DMAPP or its equivalents as the electrophile in homogeneous aqueous acidic media in the absence of enzyme to provide prenylated indole products. After establishing the bioinspired indole prenylation reaction, this was then used to achieve the synthesis of a series of natural products, namely, N-prenylcyclo-l-tryptophyl-l-proline, tryprostatins, rhinocladins, and terezine D.
A practical enantioselective total synthesis of the unnatural (+)-quinine and (−)-9-epi-quinine enantiomers, which are important organocatalysts, is reported.
The combination of carbaboranylmercuric chloride (new type of bulky Lewis acid) and silver triflate efficiently catalyzes cycloisomerization of 1,3-dienes at room temperature. The catalytic system gives allyl-substituted azacycles and cycloalkanes in excellent yields with high to complete regioselectivity.
Chiral piperidines which contain an alkyl group at C4 positions are one of the important architectures because it is appeared in several natural products. An efficient protocol for the preparation of C4-alkyl substituted chiral piperidines using secondary amine catalyzed formal aza [3+3] cycloaddition reaction with aliphatic α,β-unsaturated aldehydes and thiomalonamate derivatives is reported. In our reaction system, thiomalonamate is an excellent nucleophile and the addition of suitable acid and its amount is an important factor for the acceleration effect in organocatalytic reaction. Furthermore, water and MeOH also have an acceleration effect. These efforts lead to only 0.1 mol % catalyst loading in multigram scale synthesis for suitable reaction time. In addition, the efficient enantioselective total synthesis of (+)-α-skytanthine by using our developed reaction as key step was achieved in total 15 % yield. All carbon and nitrogen units were introduced by one step with high enantioselectivity.
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