The synthesis of a key intermediate in the total synthesis of insect antifeedant clerodanes
The synthesis of a key intermediate, 1,2,3,4,4a,5,6,7,8,8aβ-perhydro-4α-isopropyldimethylsilyloxy-4aα-isopropyldimethylsilyloxy-methyl-1α,2α-dimethyl-5-methylene-naphthalene-1β-carbaldehyde 31 , in the total synthesis of insect antifeedant clerodanes is described. The stereochemistry of this intermediate is proven by an X-ray analysis of one of its precursors e.g. 10α-acetoxy-7β-(1,3-dioxolan-2-yl)-3,3aβ,4,5,6,6aβ,7,8,9,10-octahydro-7α,8α-dimethyl-1H-naphtho[1,8aα-c] furan 25 . Crystal data: C 19 H 30 O 5 ; monoclinic, P2 1 /n, cell dimensions: a=7.9714(4), b=11.1722(4), c=19.7783(5) A, β=92.595(5) °, Z=4; conventional R-factor=0.053.