2 [4-(deca-1,8-diyl)-2,5-dioxo-2,5-dihydro-3-furanyl]acetate + H(+) = 2-[(1R,8S,14R,15R)-11-hydroxy-14,15-bis[(6E)-oct-6-en-1-yl]-3,5,9-trioxo-4,10-dioxatetracyclo[9.4.0.0(2,6).0(8,12)]pentadeca-2(6),12-dien-8-yl]acetate + CO2 — reaction