In situ generation of 2,3-allenolates in the coupling of secondary homopropargylic alcohols and aldehydes

Prins cyclization-mediated stereoselective synthesis of tetrahydropyrans and dihydropyrans: an inspection of twenty years

Functionalized tetrahydropyran (THP) rings are important building blocks and ubiquitous scaffolds in many natural products and active pharmaceutical ingredients (API). Among various established methods, the Prins reaction has emerged as a powerful technique in the stereoselective synthesis of the tetrahydropyran skeleton with various substituents, and the strategy has further been successfully applied in the total synthesis of bioactive macrocycles and related natural products. In this context, hundreds of valuable contributions have already been made in this area, and the present review is intended to provide the systematic assortment of diverse Prins cyclization strategies, covering the literature reports of the last twenty years (from 2000 to 2019), with an aim to give an overview on exciting advancements in this area and designing new strategies for the total synthesis of related natural products.

How easy are the syntheses of allenes?

This short review highlights some of the recent important developments on the synthesis of allenes and its applications on the synthesis of some allenic natural products and allenic-based optoelectronic materials.

beta'-Hydroxy-alpha,beta-unsaturated ketones: A new pharmacophore for the design of anticancer drugs. Part 2

Novel antiproliferative beta'-acyloxy-alpha,beta-unsaturated ketones were obtained by means of an iron(III)-catalyzed multicomponent domino process (ABB' 3CR). The most active derivatives displayed GI(50) values in the range of 0.5-3.9 muM against a panel of representative human solid tumor cell lines: A2780, SW1573, HBL-100, T-47D and WiDr. Analysis of cells following 24 h exposure to these drugs showed cell cycle arrest in the S and G(2)/M phase, in a dose-dependent manner. Our data indicate that the beta'-acyloxy-alpha,beta-unsaturated ketones cause permanent damage to the cells and induce apoptosis.

Antiproliferative activity of 4-chloro-5,6-dihydro-2H-pyrans. Part 2: Enhancement of drug cytotoxicity

The Prins reaction was the basis to synthesize functionalized alkyl chlorodihydropyran derivatives. The inexpensive, stable, and environmentally friendly FeCl(3) promotes the cyclization. The method represents an efficient and regioselective manner to obtain in a single step chlorovinyl-TMS oxacycles. The in vitro antiproliferative activities of the compounds were examined in the human solid tumor cell lines A2780 (ovarian cancer), SW1573 (non-small cell lung cancer), and WiDr (colon cancer). Overall, the results show an enhancement in the cytotoxicity exhibited by the new analogs when compared to their parental compounds.

β′-Hydroxy-α,β-unsaturated ketones: A new pharmacophore for the design of anticancer drugs

A series of beta'-hydroxy-alpha,beta-unsaturated ketones were prepared by means of an iron(III) catalyzed domino process. The in vitro antiproliferative activities were examined in the human solid tumor cell lines A2780, SW1573, and WiDr. The results showed that beta'-hydroxy-alpha,beta-unsaturated ketones were more potent than alpha,beta-unsaturated ketones. The best activity profiles were obtained for the derivatives bearing cyclic or branched substituents on the side chains.

The Silylalkyne-Prins Cyclization: Stereoselective Synthesis of Tetra- and Pentasubstituted Halodihydropyrans

[reaction: see text] A new type of Prins cyclization using silylated secondary homopropargylic alcohols and aldehydes yielding tetra- and pentasubstituted dihydropyrans is described. The presence of the trimethylsilyl group in the triple bond favors the Prins cyclization and minimizes the 2-oxonia-[3,3]-sigmatropic rearrangement as a competitive alternative pathway. Ab initio theoretical calculations of the species involved in the rearrangements support the proposed mechanism. The process is highly stereoselective, affording cis-dihydropyran as the only isomer.