A compound of formula (I): (I) wherein Y is, Z is OR10, NR11R11 SR11, S(O)R11 SO2R11, R10 is H, optionally substituted alkyl, optionally substituted cycloalkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted aryl, optionally substituted heteroaryl, optionally substituted heterocyclyl, CO—R11, or a protecting group, and R11 is optionally substituted alkyl, optionally substituted cycloalkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted aryl, optionally substituted heteroaryl, optionally substituted heterocyclyl, or alkoxyl; a process for making a compound of formula (I); and a process for making a prostaglandin or a prostaglandin analog using a compound of formula (I). wherein Y is