BIOMIMETIC STRATEGIES IN ORGANIC SYNTHESIS. TERPENES

The current paper represents an outline of the selected contributions to the biomimetic procedures and approaches for the synthesis of terpenes with complex structure and diverse functionalisation pattern. These include homologation strategies, cyclisations, rearrangements, as well as biomimetic remote functionalisations

CONTINUOUS EVOLUTION IN COLABORATIONS BETWEEN MOLDOVAN AND ITALIAN CHEMISTS

Moldovan chemists hosted the Italian partners in Chisinau and organized in premiere for the last 20 years an international seminar devoted to the chemistry of natural products. The seminar’s motto: New Frontiers in the Chemistry of Natural Products has addressed numerous students and researchers acting in the fields of chemistry, biology, pharmacy, genetics, biophysics as well as specialists from the R&D sector of companies with chemico-pharmaceutical profile. Following multiple solicitations coming from seminar audience, made us provide in the current issue of the “Chemistry Journal of Moldova. General, Industrial and Ecological Chemistry” a condensed abstract of the seminar presentations. We do really hope that our joint event will give further impetus to our collaboration and will also motivate other researchers from Moldova to develop partnerships with European colleagues

(-)-SCLAREOL CONVERSION IN RITTER'S REACTION CONDITIONS

The main products of sclareol (1) Ritter’s reaction in mild conditions are (8R,13R)-Labd-14(15)-en-8,13-diacetamide (2) (8R,13S)-Labd-14(15)-en-8,13-diacetamide (3) stereoisomeric on C13 atom and having unrearranged native diol skeleton. We present in the current communication the results of sclareol converting (1) into nitrogen-containing labdanes in the Ritter’s reaction conditions

Enzymatic synthesis of an indole diterpene by an oxidosqualene cyclase: mechanistic, biosynthetic, and phylogenetic implications

Petromindole (1) is an unusual indole diterpene that bears a triterpene-like carbon skeleton, suggesting biogenesis from 3-(-oxido-geranylgeranyl)indole (4). We found that lupeol synthase (LUP1) from Arabidopsis thaliana cyclizes 4 to 1. Chiral HPLC comparisons of racemic 1 (from biomimetic cyclization of N-pivaloyl-4) with the LUP1 product and authentic 1 established the absolute stereochemistry of petromindole (3S) as that of cyclic triterpenes. Quantum mechanical calculations and conformational analysis of intermediates in the cyclization of 4 to 1 indicated that petromindole biosynthesis differs fundamentally from that of other indole diterpenes. This analysis revealed that radarins also originate from cyclization of 4 but undergo a backbone rearrangement rather than annulation to indole. The combined results support our hypothesis that native fungal petromindole synthase evolved from a pentacyclic triterpene synthase distant from most other indole diterpene synthases

Enantiospecific, biosynthetically inspired formal total synthesis of (+)-Liphagal

A biosynthetically inspired synthesis of (+)-liphagal has been achieved from (+)-sclareolide in 13 steps (9% overall yield). The key step is a biomimetic ring expansion of a highly stabilized benzylic carbocation, which generates the seven-membered ring and the benzofuran of the natural product in a single cascade reaction.Jonathan H. George, Jack E. Baldwin and Robert M. Adlingto