A new synthesis of tricyclic sesquiterpene (±)-sterpurene

Application of (4+3) cycloaddition strategies in the synthesis of natural products

This review summarizes the applications of (4+3) cycloadditions, both classical and formal, in the syntheses of natural products in the last two decades.

Cycloaddition of Spiroepoxycyclohexa-2,4-dienones, Radical Cyclization and 1,3-Acyl Shift in Excited State: Aromatics to Sterpuren-4-one

A stereoselective route to sterpuren-4-one from a simple aromatic precursor is presented. Oxidative dearomatization, π⁴s + π²s cycloaddition of 6,6-spiroepoxycyclohexa-2,4-dienones with ethyl acrylate, radical cyclization and 1,3-acyl shift in excited state are the important aspects of our approach. An interesting effect of a remote substituent on radical cyclization has also been presented.

Recent Advances in the Synthesis of Cyclobutanes by Olefin [2 + 2] Photocycloaddition Reactions

The [2 + 2] photocycloaddition is undisputedly the most important and most frequently used photochemical reaction. In this review, it is attempted to cover all recent aspects of [2 + 2] photocycloaddition chemistry with an emphasis on synthetically relevant, regio-, and stereoselective reactions. The review aims to comprehensively discuss relevant work, which was done in the field in the last 20 years (i.e., from 1995 to 2015). Organization of the data follows a subdivision according to mechanism and substrate classes. Cu(I) and PET (photoinduced electron transfer) catalysis are treated separately in sections 2 and 4 , whereas the vast majority of photocycloaddition reactions which occur by direct excitation or sensitization are divided within section 3 into individual subsections according to the photochemically excited olefin.

Photochemical reactions as key steps in natural product synthesis

Photochemical reactions contribute in a significant way to the existing repertoire of carbon-carbon bond-forming reactions by allowing access to exceptional molecular structures that cannot be obtained by conventional means. In this Review, the most important photochemical transformations that have been employed in natural product synthesis are presented. Selected total syntheses are discussed as examples, with particular attention given to the photochemical key step and its stereoselectivity. The structural relationship between the photochemically generated molecule and the natural product is shown, and, where necessary, the consecutive reactions in the synthesis are illustrated and classified.

Intramolecular thermal allenyne [2 + 2] cycloadditions; facile construction of the 5-6-4 ring core of sterpurene

A variety of 1-allenyl-2-propargyl-substituted cyclopentanol derivatives were found to undergo facile intramolecular microwave-assisted 2+2 alleneyne cycloaddition reactions to generate tricyclic 5-6-4 ring systems present in the sterpurenes.

A 4+3 cycloaddition approach to the synthesis of (+/-)-sterpurene

A synthesis of the sesquiterpene sterpurene is presented. Key steps include a 4+3 cycloaddition reaction and a quasi-Favorskii rearrangement. [reaction--see text]