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Identifier

000311103

Title

Βιομιμητική κυκλοποίηση τερπενοειδών με εγκλωβισμό στο ζεόλιθο NaY

Alternative Title

Biomimetic cyclization of terpenoids within zeolite NaY

Author

Τσαγκαράκης, Κωνσταντίνος Μηνά

Thesis advisor

Στρατάκης, Μανόλης

Abstract

In the present Thesis was studied, for the first time in the literature, the ability of the acidic porous materials, such as zeolites NaY and HY in catalyzing the biomimetic cyclization of terpenoids under confinement conditions. The results can be summarized as follows: A. Small terpenes, such as geranyl or neryl derivatives, cyclize readily to form primarily γ-cyclogeranyl compounds in >97% yield. The most impressive result was the cyclization of geranylacetone to form the natural product α-ambrinol in up to 75% yield. In addition, the natural product nanaimoal was synthesized in a few steps and in a biomimetic manner using as key reaction the intrazeolite cyclization of farnesal. B. The mechanism of terpene cyclization under zeolite confinement was studied through studying the product stereochemistry arising from geranyl acetate labelled at the C6 or C8 respectively. The results are consonant with a concerted mechanism in which preorganization of the substrate is necessary to achieve cyclization. C. Epoxy terpenes cyclize very fast under NaY confinement to form primarily, in a highly stereoselective manner, monocyclization products (exo-methylenic cycloexanols) in appreciable yields. D. The mechanism of epoxy terpenes cyclization within NaY occurs via a concerted mechanism, as probed by studying the stereochemistry of a selectively labeled epoxide at the gem-methyl group. Ε. Finally, several α-cyclogeranyl derivatives, obtained from the intrazeolite cyclization of geranyl compounds reacted with singlet oxygen to form one out of the three possible regioisomers in up to 97% diastereoselectivity.

Language

Greek

Subject

Green chemistry

Heterogeneous catalysis

Nanaimoal

Natural products

Photooxidation

Terpenes

Zeolite

Ετερογενής κατάλυση

Ζεόλιθος