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Studies on a cycloisomerization reaction of 2‐prenylated‐2H‐pyrans towards cis‐fused tetrahydro‐6H‐benzo[c]chromene systems (reduced cis‐THC analogues) are reported. The transformation is catalyzed by iron chloride and proceeds with the formation of two new bonds and two stereocenters diastereoselectively. The same catalyst also promotes the formation of these products via a one‐pot tandem Knoevenagel condensation of 1,3‐cyclohexanediones and citral or farnesal aldehydes, followed by cycloisomerization establishing a direct assembly of this important scaffold. [ABSTRACT FROM AUTHOR]

The chemistry of phytocannabinoids has witnessed renewed interest these last decades as a consequence of reduced restrictions, research on the endocannabinoid system and the development of approved therapeutic treatments based on cannabinoids. The medicinal cannabinoid market constitutes a prolific scenario in current medicine. Most studies, however, have focused on only two major components of Cannabis sativa L., namely, cannabidiol (CBD, 2) and (-)-Δ9-trans-tetrahydrocannabinol (Δ9-trans-THC, 6a), the latter being the main psychoactive compound of this plant. The cis-diastereoisomer of Δ9-trans-THC, Δ9-cis-THC, although also present in the same plant, has been less investigated in terms of biological, medicinal and synthetic perspectives. Interestingly, the cis-fused tetrahydrobenzo [c]chromene motif present in Δ9- cis-THC is embedded in many other natural products which also exhibit interesting biological activities such as anticancer, antifungal, and antiparasitic. This review discloses synthetic approaches that have been established towards the cis-fused tetrahydroisochromene system of Δ9-cis-THC. [ABSTRACT FROM AUTHOR]

The article presents charts illustrating chemical compounds, nuclear magnetic resonance (NMR) and spectrum analysis.

The synthesis of the biologically active alkaloid huajiaosimulne, isolated from the roots of Zanthoxylum simulans, is reported. The natural product was assembled from simple commercial reagents via initial domino Knoevenagel/oxa-6π-electrocyclization followed by epoxidation and an epoxide/ketone rearrangement promoted by Zn(OTf) 2 . In vitro cytotoxicity assays identified natural products huajiaosimuline and simulansine as moderate antiproliferative agents against murine colon cancer CT26 cells., (© 2024 Wiley‐VHCA AG, Zurich, Switzerland.)

A stereoselective multicomponent reaction involving Meldrum's acid, a conjugated dienal, and an alcohol is reported. Valuable cyclopenta[ b]furan-2-ones are obtained as products of this straightforward transformation, which is accompanied by the formation of four stereocenters, two new cycles, and four new bonds (two C-C and two C-heteroatom). A reaction mechanism was elaborated involving an initial Knoevenagel condensation followed by cycloisomerization and eventual fragmentation.

A new cascade pathway viable for Knoevenagel chemistry that involves the coupling between 1,3-dicarbonyl systems and α,β,γ,δ-unsaturated aldehydes has been developed. The process comprises the combination of a classic aldol-type condensation and a rare spontaneous metal-free cycloisomerization, representing a convergent and innovative approach for the stereoselective synthesis of cyclopenta[b]furan-type derivatives. The scope and limitations with respect to both reaction partners and mechanistic features were investigated. Meaningfully, our study provides valuable guidance concerning the structural and electronic effects controlling the reactivity of conjugated polyene carbonyl systems., (Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)