The radical decarboxylation-sulfoxide cycloelimination of 2'-pyridylth
io esters formed from a series of podocarpic acid derivatives gives De
lta(4(18))-alkenes in high yield. An exception is the 13-nitro acid (2
) which affords a thiohydroxamic ester (28), the relative stability of
which is attributed to inhibition of the radical chain reaction by th
e nitro group. The stereochemistry of the pyridyl sulfide (18) has bee
n confirmed by X-ray crystallography.