[formula: see text] Compounds that induce the synthesis of nerve growth factor (NGF) are of interest as alternatives to the administration of the native peptide. We have initiated a program to study the NGF synthesis stimulating activity of the erinacine and scabronine diterpenes. Herein, we report an approach to the core cyathin system by sequential application of an oxidative coupling and [4 + 3] cycloaddition.

No abstract

The preparation of annulated furan systems as key synthetic intermediates through the application of a two-step annulation involving an electrochemical ring closure between a furan and a silyl enol ether has been studied. The reaction was shown to be quite general for the formation of six-membered rings in good yields and was tolerant of a variety of different functional groups. The ring closure was highly stereoselective, leading to the formation of cis-fused systems. Cyclic voltammetry and probe molecules were used to gain mechanistic insight into the reaction. These studies suggested that the key ring closure involved an initial oxidation of the silyl enol ether to a radical cation followed by a furan-terminated cyclization.

[reaction: see text] A two-step electrochemical annulation has been developed for the preparation of fused furans. The process involves an initial conjugate addition of a furyethyl cuprate and trapping of the enolate as the corresponding silyl enolether. The second step of the annulation involves the anodic coupling of the furan and the silyl enol ether to form a six-membered ring.

Synthesis of Annulated Furans. -A general and effective method to prepare benzofuran derivatives is developed. The key step is electrochemical cyclization of silyl enol ethers of type (IV). It proceeds with high cis selectivity and tolerates a range of functional groups. -(SPERRY, J. B.; WHITEHEAD, C. R.; GHIVIRIGA, I.; WALCZAK, R. M.; WRIGHT*, D. L.; J. Org. Chem. 69 (2004) 11, 3726-3734; Dep. Chem., Dartmouth Coll., Hanover, NH 03755, USA; Eng.) -Jannicke 39-099

The first step of the title process involves the formation of furylethyl cuprate and its reaction with cyclic enones in the presence of TmsCl to give the corresponding intermediate silyl enolethers. The second step involves the intramolecular anodic coupling under constant current conditions to give fused furans. The method can be expanded to the reaction of electron-rich benzoid ring present in compound (VI). Enone (XII), obtained by oxidative rearrangement, can be also transformed into fused furans by addition of groups to the enone prior to the electrochemical cyclization. -(WHITEHEAD, C. R.; SESSIONS, E. H.; GHIVIRIGA, I.; WRIGHT*, D. L.; Org.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.