studies in terpenoids and lachnanthocarpones

Abstract

The thesis entitled “Synthetic Studies in Terpenoids and Lachnanthocarpones” is divided into two parts and consists of five chapters. Chapters 1–3 constitute Part I, and Chapters 4–5 are included in Part II.

Chapter 1 The first total synthesis of sydowic acid, a phenolic sesquiterpenoid isolated from Aspergillus sydowi, is described. 4-(2 Hydroxy 4 methylbenzoyl)butanoic acid was prepared by the Friedel–Crafts reaction of m cresol with glutaric anhydride. Grignard reaction on its methyl ester with methylmagnesium iodide, followed by cyclodehydration, furnished 2 hydroxycurcumene ether, viz., 2,6,6 trimethyl 2 (2 hydroxy 4 methylphenyl)tetrahydropyran. The acetate of 2 hydroxycurcumene ether, upon oxidation with alkaline permanganate or treatment with N bromosuccinimide followed by hydrolysis, gave (+)-sydowic acid.

Chapter 2 A useful approach developed for constructing the 1 aryl 1,2 dimethylcyclopentane skeleton is illustrated. It involves intramolecular insertion into a benzylic C–H bond by a carbenoid derived from a diazoketone. This is exemplified in the synthesis of 2,3 dimethyl 3 p tolylcyclopentanone from 4 p tolyl n valeric acid via 2 diazo 6 p tolylheptan 4 one, the precursor of the carbenoid species.

Chapter 3 An attempted synthesis of 2 hydroxycuparene is described. The preparation of several synthetic intermediates-

2,2,3 trimethyl 3 (3 methoxy 4 methylphenyl)propionic acid and 2,2 dimethyl 3 (3 methoxy 4 methylphenyl)but 3 en 1 ol

-is outlined. Results of attempted conjugate addition to certain unsaturated cyano esters are also presented.

Chapter 4 This chapter describes the alcoholysis of p furfurylidene derivatives of arylmethyl ketones. The conversion of aryl p 2 furylvinyl ketones to ethyl p (5 aryl 2 furanol)propionates and their corresponding free acids via acid catalysed ethanolysis is illustrated. The present method is simple and economical compared to existing procedures.

Chapter 5 This chapter deals with the synthesis of p (7 phenyl 1 tetralyl)propionic acid, a key intermediate for synthesizing several naturally occurring phenalenone pigments found in Lachnanthes tinctoria and Xiphidium caeruleum. Ethyl 7 phenyl 1 tetralyl acetate, prepared by the Reformatsky reaction of 7 phenyl 1 tetralone with ethyl bromoacetate, has been elaborated into p (7 phenyl 1 tetralyl)propionic acid.