Stereospecific Syntheses from Podocarpic Acid

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ABSTRACT

The t r i t e r p e n e precursor, 12-nethoxypodocarpa-8,17

,

^13-trien-

3-one (46)*, h a s been p r e p a r e d via the 3a-alcohol (48) formed by opening of t h e 3u,&-epoxide (1 3) w i t h l i t h i u m diethylamide.

The t o t a l synthesis of t h e methyl ether of t h e ratural product, (+)-hinolcione, has been achieved by a similar sequence

involving prior addition of an isoprqyl group at C 13 of t h e methoxy acid (4) ( Scheme 1 )

.

A study of the boron t r i f l u o r i d e rearrangements of t h e three epoxides (1 2), (1 3 ) , and (14), has been made using benzene and dimethyl sulphoxidc as solvents.

The stereochemistry of a series of 6-bromo-7-cxo

derivatives of diterpenoids possessing an aromatic r i n g 4 is discussed and the assignment of configuration of the 6-bromo substituents from n.m.r. and n.0.e. d a t a is examined.

+ The numbering system used throughout this thesis i s t h a t proposed by J. iJ. Rowe (personal communication to Professor R e C. ~ a m b i e ) in "The Common and Systematic Nomenclature of Cyclic DiterpenesH, 3rd Revision, O c t . 1968, to be submitted to the IUPAC Commission on Organic Nomenclature.

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ii.

A preliminmy investigaticn i n t o ^thep o s s i b i l i t y of preparing a 9a-methyl s t e r o i d a l analogue by addition of a cyclopentjnone ring across p o s i t i o n s 3 and ⁴of ring-A of t h e podocarpic system is also reported.

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