Overall, these findings indicate that two catalytic reactions are involved in the formation of the novel type of polyesters reported herein (Fig. ): (i) the ruthenium-catalyzed hydrogen transfer ester metathesis that results in chemically modified ester groups, and (ii) the base-catalyzed transesterification that facilitates a rapid chain exchange and equilibrates the system towards the most stable sequence(s). Both reaction involve an initial cleavage of an ester group and lead in case of (i) to a cleaved (aldehyde) resting state, which results in overall reduced molecular weights.