A novel alpha-n-propyl-substituted seven-membered cyclic carbonate (alpha-n-Pr-TEMC) was synthesized and used to prepare its homopolymer and statistical copolymer with epsilon-caprolactone (epsilon-CL). Homopolymerization via Sn(Oct)2-catalyzed ring-opening polymerization proceeded in a controlled manner. The alpha-n-propyl substituent effectively moderated the monomer's reactivity, enabling its statistical copolymerization with epsilon-CL, as confirmed by NMR analysis. DSC curves demonstrated transition from a semi-crystalline homopolymer to a copolymer with suppressed crystallinity. This work demonstrates alpha-n-Pr-TEMC's utility as a comonomer for tailoring the properties of biodegradable polyesters.