Abstract The synthesis of new derivatives of prostaglandins F 2α and E 2 XIIa, b-XVa, b and XXa, b-XXIIIa, b containing the furan or thiophene nucleus in the upper chain has been accomplished starting from [3aα, 4α, 5β, 6aα]-(±)-hexahydro-5-hydroxy-4-((E)-(3α)-hydroxy- 1-octenyl)-2H-cyclopenta [b] furan-2-one (Ia) and [3aα, 4α, 5β, 6aα]-(±)-hexahydro-5- hydroxy-4-[4-(3-chlorophenoxy)-(3α)-hydroxy-1-butenyl] cyclopenta [b] furan-2-one (Ib). ...