Themed collection Polycyclic Reactions in Synthesis and Biosynthesis

In the past five years, there have been remarkable advances in the study of β-amyrin synthase. This review outlines the catalytic mechanism and substrate recognition in β-amyrin biosynthesis, which have been attained by the site-directed mutagenesis and substrate analog experiments.

A review of computational studies of the related biosyntheses of steroids and hopenes reported during the last two decades is presented.

Isoprenoid precursors readily undergo (poly)cyclization in electrophilic reaction cascades, presumably as internal addition of the carbon–carbon double-bonds from neighboring isoprenyl repeats readily forms relatively stable cyclohexyl tertiary carbocation intermediates.

α,β-Unsaturated acylammonium salts are useful dienophiles enabling highly enantioselective and stereodivergent Diels-Alder-initiated organocascades with furan-based dienes.

A terpene cyclases from Streptomyces malaysiensis was characterised as (+)-isoafricanol synthase and its mechanism was investigated using isotopically labelled substrates.

The polycyclisation of polyeneynes catalyzed by gold(I) has been extended for the first time to the simultaneous formation of up to four carbon–carbon bonds, leading to steroid-like molecules with high stereoselectivity in a single step with low catalyst loadings.

Simple activation of readily available ynamides under acidic conditions triggers an unprecedented cationic polycyclization yielding highly substituted polycyclic nitrogen heterocycles.

Radical cyclisation cascades triggered by electron-transfer to amide-type carbonyls using SmI₂–H₂O–LiBr, result in the selective construction of quaternary carbon stereocentres.

This study focusses on the [2 + 2]-photocycloaddition of a symmetric polyenic system tethered by an aryl bis-sulfide or sulfone platform.

Substituent effects reshape the potential energy surfaces for radical homoallylic expansion/fragmentation cascades that transform alkenyl isonitriles into N-heteroaromatics

The squalene cyclase of Tetrahymena pyriformis cyclizes 2,3-dihydrosqualene to euph-7-ene; after truncation of the substrate, “tirucall-7-enes” are formed.

The results of density functional theory calculations on thiyl radical-promoted polycyclization to form dodecahedrane are described.

A diastereoselective, gold-catalyzed cascading cycloisomerization of alkylidene cyclopropane bearing 1,5-enynes that terminates in a cyclo-addition of aldehydes has been developed.