Formation of 4-Hydroxy-3,7-dimethyl-2,6-octadienal (5-Hydroxycitral) from 3,7-Dimethyl-2,6-octadienal (Citral) and its Biological Activity against Sarcoma 180
Obtention of 2,2-(diethoxy) vinyl lithium and 2-methyl-4-ethoxy butadienyl lithium by arene-catalysed lithiation of the corresponding chloro derivatives. Synthetic applications
precursors 5 and 6 instead of the less stable corresponding bromo derivatives 3 and 4. Condensation with carbonyl compounds leads to interesting synthetic applications such as a two steps synthesis of retinal 13 from β-cyclocitral 10.
The potassium dienolate of prenal obtained by treatment of the corresponding dienoxysilane with tBuOK was reacted with enaldehydes. In all cases a gamma-specific reaction occurs. According to the reaction conditions gamma;1,2 or a gamma;1,4 coupled product was selectively obtained with enals. The gamma;1,2 reaction provided an efficient prenylation procedure. A short two-step synthesis of retinal is described. (C) 1998 Elsevier Science Ltd. All rights reserved.