Chemoenzymatic Synthesis of the Enantiomer of 4,12-Dihydroxysterpurene, the Structure Assigned to a Metabolite Isolated from the Culture Broth of Stereum purpureum

Controlling Cyclic Dienamine Reactivity in Radical tert-Alkylation for Molecular Diversity to Synthesize Multicyclic Compounds Possessing a Quaternary Carbon

Synthesis of diverse sterically congested molecules from a single important intermediate is one of the ideal synthetic strategies in organic synthesis. In this paper, we found that γ-oxoalkyl substituted cyclohexenone derivatives (OAC) possessing a quaternary carbon are a useful key intermediate to derive both congested fused [5,6] rings and spirocycles. For this purpose, we have established an efficient synthetic method to obtain OAC by tertiary alkylation of β-methylcyclohexenone derivatives using α-bromocarbonyl compounds as a tertiary alkyl source. The key to the success of this reaction is controlling the reactivity of the dienamine intermediate. While there have been many reports on enamine reactions, dienamine reactions have not been well studied. Herein, we report controlling reactivity of dienamines and molecular diversification from OAC.

Photoinduced Decarbonylative Rearrangement of Diazabicyclo[2.2.2]Octenones: A Photochemical Approach of Diazabicyclo[4.1.0]heptene Skeleton from Masked o-Benzoquinone

We report a photoinduced decarbonylative rearrangement of diazabicyclo[2.2.2]octenone in the facile synthesis of a functionalized diazabicyclo[4.1.0]heptene skeleton, a unique derivative of the hydropyridazine type structure which could be found in a variety of biologically active natural products. The scope of functional group compatibility in the photoreaction was examined by taking advantage of the easy access of the heterobicyclo[2.2.2] structure from the Diels-Alder reaction of masked o-benzoquinones. 4-Phenyl-1,2,4-triazoline-3,5-dione served as the dienophile which provided the adjacent N-N unit in hexahydropyridazine-type products of subsequent photorearrangement.

The Application of Dioxygenase-Based Chemoenzymatic Processes to the Total Synthesis of Natural Products

This Minireview describes the exploitation of certain enzymatically derived, readily accessible, and enantiomerically pure cis-1,2-dihydrocatechols as starting materials in the chemical synthesis of a range of biologically active natural products, most notably sesquiterpenoids and alkaloids.

Spiro 1,3-indandiones: intramolecular photochemical reactions of carbonyl groups with carbon–carbon double bonds

Spiro-1,3-indandiones involving a double CC bond undergo photochemical intramolecular reactions affording a variety of polycyclic products.

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.

Chemoenzymatic Total Syntheses of the Enantiomers of the Protoilludanes 8-Deoxydihydrotsugicoline and Radudiol

Chemoenzymatic and stereoselective total syntheses of the non-natural enantiomeric forms of the recently isolated protoilludane natural products 8-deoxydihydrotsugicoline (1) and radudiol (2) (viz. ent-1 and ent-2, respectively) are reported. The key steps involve the Diels-Alder cycloaddition of cyclopent-2-en-1-one to the acetonide derived from enantiomerically pure and enzymatically derived cis-1,2-dihydrocatechol 3, elaboration of the resulting adduct to the tricyclic ketone 12, and a photochemically promoted rearrangement of this last compound to the octahydro-1H-cyclobuta[e]indenone 13.

Photoinduced Decarbonylative Rearrangement of Bicyclo[2.2.2]Octenones: Synthesis of the Marasmane Skeleton

The marasmane sesquiterpenoid structure can be found in the skeleton of a variety of natural products bearing interesting bioactivity. The unique fused-5,6,3-tricyclic ring structure, in which the rings are cis-fused and the five- and three-membered rings are mutually trans, provides a synthetic challenge for organic chemists. In this work, we took advantage of the photoinduced decarbonylative rearrangement of bicyclo[2.2.2]octenone to develop a new methodology for construction of the highly functionalized fused-5,6,3-tricyclic ring structure in a concise reaction sequence.