New constituents of the leaves of Alpinia flabellata

Synthesis of novel 1,2,3-triazole-substituted tomentosins

A series of 1,2,3-triazole-containing tomentosin scaffolds was obtained from tomentosin 1. The synthesis involved a Michael addition of trimethylsilylazide on the α-methylene-γ-lactone function of the natural sesquiterpene lactone 1 to give the diastereoisomers 2 and 3, which were readily separated by column chromatography. These compounds underwent copper-catalyzed Huisgen 1,3-dipolar cycloaddition with various terminal alkynes to provide compounds 4a–h and 5a–h in good yields.

An overview of chemical constituents from Alpinia species in the last six decades

Alpinia species is one of the most important genera of the Zingiberaceae family. Up to 2015, 544 compounds with various bioactivities were isolated, the major components are diarylheptanoids (143) and sesquiterpenoids (132).

CO2-activation for γ-butyrolactones and its application in the total synthesis of (±)-heteroplexisolide E

An efficient nickel(0)-catalyzed highly regio- and stereoselective hydrocarboxylation of homopropargylic alcohols with ZnEt(2) in the presence of CO(2) (1 atm, balloon) to synthesize α-alkylidene-γ-butyrolactones is described. The catalyst is highly active and can be applied for the synthesis of (optically active) mono- or bicyclic α-alkylidene-γ-butyrolactones with excellent regio- and stereoselectivity and good functional group tolerance. The potential of the reaction has been demonstrated in the first synthesis of (±)-heteroplexisolide E.

Highly selective nickel-catalyzed methyl-carboxylation of homopropargylic alcohols for α-alkylidene-γ-butyrolactones

A first practical Ni(0)-catalyzed highly stereoselective methyl-carboxylation of homopropargylic alcohols with ZnMe(2) and CO(2) for the efficient synthesis of α-alkylidene-γ-butyrolactones is described. The reaction may be applied to other alkynols.

Cross-Metathesis between α-Methylene-γ-butyrolactone and Olefins: A Dramatic Additive Effect

[reaction: see text] Olefin cross-metathesis between alpha-methylene-gamma-butyrolactone and terminal olefins is described. Moderate to excellent yields of alpha-alkylidene-gamma-butyrolactones were obtained with high E-stereoselectivity in the presence of low catalyst loading in refluxing CH2Cl2. In addition, the use of various additives was found to have a dramatic effect on the efficiency of the cross-metathesis (CM) process by circumventing the formation of the isomerized byproduct.

New flavonol-phenylbutadiene adducts from the leaves of Alpinia flabellata

Two new flavonol-phenylbutadiene adducts, rel-5-hydroxy-7,4'-dimethoxy-2' 'S-(2,4,5-trimethoxy-E-styryl)tetrahydrofuro[4' 'R,5' 'R:2,3]flavanonol (1) and rel-5-hydroxy-7,4'-dimethoxy-3' 'S-(2,4,5-trimethoxy-E-styryl)tetrahydrofuro[4' 'R,5' 'R:2,3]flavanonol (2), were isolated from the leaves of Alpinia flabellata, along with three known compounds, 2,4,5-trimethoxybenzoic acid, 2,4,5-trimethoxycinnamic acid, and 5-hydroxy-3,7,4'-trimethoxyflavone. The structures of 1 and 2 were determined by spectroscopic interpretation.