(E,E)-Methyl sorbate (MS) and (E,E)-ethyl sorbate (ES), i.e., methyl 2,4-hexadienoate and ethyl 2,4-hexadienoate, underwent anionic polymerization in toluene at -60 to 0degreesC in the presence of organoaluminum Lewis acids. The NMR, wide-angle X-ray diffraction (WAXD), and semiempirical molecular orbital calculation demonstrated that 1,4-trans-threo-disyndiotactc polymerization occurred (tritactic polymerization). Coordination of methylaluminum bis(2,6-di-tert-butyl-4-methylphenoxide) (MAD) (MAD/t-BuLi = 3) played three important roles, stabilization of the propagating anion, the activation of the monomer, and dissociation of tert-butyllithium (t-BuLi) aggregated in toluene to give polymers with relatively narrow molecular weight distribution (M-w/M-n = 1.3) using t-BuLi-(-)-menthyl ethyl ether (MEE) complex as the initiator. Hydrogenations of poly(MS) and poly(ES) with p-toluenesulfonylhydrazide (TSH) produced head-to-head (H-H) poly(propylene-alt-methyl acrylate) and poly(propylene-alt-ethyl acrylate), respectively, which enabled us to evaluate the stereochemistry including diastereoselectivity and stereoregularity of poly(alkyl sorbate)s in detail. The polymer from t-BuLi-MEE/MAD initiator system (at -60degreesC) showed the highest stereospecificity, i.e., threo(99%)-disyndiotacticity(95%). The glass transition temperature of the threo poly(MS) is 27degreesC with melting endotherm at 102degreesC. The thermal property depends on the stereochemistry. Furthermore, we indicate that the polymerization proceed via "alternating turning over polymerization (ATOP)" mechanism, in which Lewis acid coordinated monomers are inserted into the propagating center with alternating turning over.