Synthetic studies utilizing podocarpic acid

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ABSTRACT

The k e t oe st e r

,

3-ethoxycarbonyl-12-met hoxy-5 pH-1 8,19-bi snor- podocarpa-8,11,13-trien-4-one (80)

, *

has been prepared from

1 2-hydroqrpodocarpa-8,11 ,I 3-trien-l g-oic acid (1 )

,

v i a t h e C

4

ketones (76) and (77). Both of these isomers were obtained from t h e nethoxyallcene (1 1 )

,

which w a s i s o l a t e d i n a pure form during s e l e c t i v e e p o ~ d d a t i o n of the methoxyalkene mixture (1 1

-

¹

3)

obtained from t h e decarboxylat i o n of 1 2-metho~odocarpa-8,11 ,I 3-trien-19-oic acid (2) with lead t e t r a a c e t a t e .

This r e a c t i o n has been investigated, and a mechanism accounting f o r t h e formation of n o n d e c a r b o x ~ l ~ t i o n products i s proposed.

The unsaturated k e t o e s t e r (1 02) was prepared i n low y i e l d v i a t h e s a t u r a t e d C 1 2 ketone (24)

,

obtained .From 1 2-hydroqodocarpa-8, I 1 ,I 3- trien-19-oic acid ( 1 ) by Birch reduction of t h e aromatic ring.

A number of ring A epoxi.de d e r i v a t i v e s of t h e a c i d (1) were prepqared and cleaved by a v a r i e t y of r e s e n t s t o give t h e 3-oxygenated d e r i v a t i v e s (1

45),

(1 4 6 ) , and (1 52), together with compounds possessing a contracted r i n g A. Some rin: I3 lactone d e r i v a t i v e s of t h e a c i d (1)

*

The numbering used throughout t h i s t h e s i s i s t h a t proposed by J.W. Rowe (personal communication t o D r . R. S. ~ a m b i e ) i n 'The Common and

Systematic ITomenclature of C ~ c l i c D i t e r p n e s ' , 3rd Revision, Oct. 1968, t o be submitted t o the IUPAC Colmission on Organic Nomenclature.

iii

were re pa red, and t h e i r stereochemistry a.nd conformation were

determined by n.m.r. s p c t r o s c o p y . The conformation of some ring B- s u b s t i t u t e d d e r i v a t i v e s was a l s o determined by n.m.r. methods.

The brominat i o n of some 7-lre t opodocarpa-8, 1 1

,

¹ 3-triene d e r i v a t i v e s vas i n v e s t i g a t e d , and reasons a r e advanced f o r t h e non-stere o s p e c i f i c r e a c t i o n s observed i n some cases.