The reaction of N-phthaloyl-L-leucine acid chloride (1) with isoeugenol (2) was carried out in chloroform, and novel optically active isoeugenol ester derivative 3 as a chiral monomer was obtained in high yield. Compound 3 was characterized by H-1-NMR, IR, and mass and elemental analysis and then was used for the preparation of model compound 5 and polymerization reactions. 4-Phenyl-1,2,4-triazoline-3,5-dione, PhTD (4), was allowed to react with compound 3. The reaction is very fast and gives only one diastereomer of 5 via Diels-Alder and ene pathways in quantitative yield. In order to explain this diastereoselectivity, a nonconcerted two-step mechanism involving benzylic cation (BC) and aziridinium (AI) have been proposed for the Diels-Alder and ene reactions, respectively. The polymerization reactions of novel monomer 3 with bis(triazolinedione)s [bis(p-3,5-dioxo-1,2,4-triazolin-4-ylphenyl)methane (8) and 1,6 bis(3,5-dioxo-1,2,4-triazolin-4-yl)hexane] (9)] were performed in N,N-dimethylacetamide (DMAc) at room temperature. The reactions are exothermic, fast, and gave novel optically active polymers 10 and 11 via repetitive Diels-Alder-ene polyaddition reactions. These polymers have inherent viscosities in a range about 0.18-0.22 dL/g. Some physical properties and structural characterizations of these new polymers have been studied and are reported.