Abstract Furan-2-ylmethyl 2-oxoacetates 1a, b, in which the furan ring and the carbonyl moiety were embedded intramolecularly, were synthesized from commercially available furan-2-ylmethanol and their photochemical reaction (hν> 290 nm) was investigated. Twelve- membered macrocyclic lactones 2a, b with C i symmetry including two oxetane-rings, which are the Paternò–Büchi dimerization products, were isolated in ca. 20% yield. The ...