Plant growth regulators in Eucalyptus grandis. IV. Synthetic approaches to G-regulator analogues

Abstract

A new synthetic approach is described to the plant growth regulators of the hexahydrobenzo[e]- 1,2-dioxin group (the G-regulators of Eucalyptus grandis). Condensation of 1,3-diketones with aldehydes under Lewis acid catalysis gives, in good yield, the 1 : 2 adducts (4H-1,3-dioxins); these are simultaneously cleaved and (with some exceptions) oxidized on silica gel to the desired structure. In this way synthesis of a number of G-regulator analogues of similar physiological activity has been achieved.