Coumarins of murraya species and synthetic studies on pheromones

Abstract

This thesis consists of two parts.

Part I describes studies on Murraya gleniei, whose extracts showed insecticidal activities.

M. gleniei leaves contained a new coumarin, 5,6, 7-trimethoxy-8-(2’,3’-dihydroxyisopenty!)coumarin (murragleinin) and eight more coumarins, phebalosin, meranzin, epi-sibiricin, murralongin, meranzin hydrate, scopoletin, murrangatin, and epi-mexoticin, together with skimmianine, exoticin and stigmasterol. Its root bark contained the new coumarins, 5, 7-dimethoxy-8-(3’-methyl- 1’-butenyl)coumarin (gleinene), 5, 7-dimethoxy-8-(3’-methyl- 1’,3’-buta-dienyl)coumarin (gleinadiene), a new dimeric coumarin, 2’,3-di(5",7"-dimethoxycoumarin-8"-y1l)-1,4,- dimethy1-4-(1’-ethenyl)cyclohexene with eight coumarins found in the leaves, four more coumarins, toddalenone, coumurrayin, omphamurin and threo-murrangatin and two sesquiterpenoids, bulnesol and quaiol. The stem bark of M. gleniei contained the dimeric coumarin and seven other coumarins present in the root bark havethew with one more coumarin, umbelliferone.

The insecticidal activity of these extracts was due to the presence of phebalosin.

The acid catalysed rearrangements of (-)-phebalosin, (t)-erythro-murrangatin, threo-murrangatin and epi-mexoticin Beidica. (-)-Phebalosin gave (-)-murrangatin and urralongin, while (t)-erythro-murrangatin gave murralongin, esting that the structure of murralongin needed revision 7-methoxy-8-(1’-formy1]-2’-methylprop-1’-enyl])coumarin. ‘eo-Murrangatin, however, gave with acid, 3-formyl-3-methyl- 2-(7'-methoxycoumarin-8’-yl)-5S-isopropyltetrahydrofuran. The thro- and threo- isomers behaved differently with acidic cetone, the former giving an acetonide while the latter gave 3-formy1-2-(7?-methoxycoumarin-8’ -yl)-3,5,5-trimethyltetra- ee Differences in reactivity are explained on the _stereoelectronic requirements of the pinacol rearrangement. Acid rearrangement of epi-mexoticin gave 2'[1',1'-dimethyl-2’- 5", 7"-dimethoxycoumarin-8"-y1)ethyl1-4-[5", 7"-dimethoxy - ~ coumarin-8"-y1)methy1]-5,5-dimethy1-1,3-dioxalane.

Part II of the thesis discusses the synthesis and attempted synthesis of some insect pheromones.

trans- P-Farnesene was synthesized from 2-methyl- 6-methylene-1, 7-octadien-3-01 in four steps in 57% yield. An intermediate in the synthesis was converted into 2,6-dimethyl- . 10-methylene-1,6,14-dodecatrien-3-0l in 45% yield in an attempt to synthesize f-sinensal.

An attempted synthesis of lineatin from carvone using an intramolecular photosensitized (2+2) addition for the formation of the cyclobutane ring gave hydroxylineatin in 7 steps in an overall yield of 6%.