Abstract Using (2 E)-4, 4-dimethoxy-2-butenal as starting compound, methods were developed for synthesis of (2 E, 4 E)-and (2 E, 4 Z)-dimethoxyalkadienes. Deacetalization of the latter gives with high yield the corresponding dienals which are naturally occurring compounds and also synthons for preparation of conjugated dienes as key compounds for building up other natural products.