The iodohydrins 2, 4, and 5 were prepared by the ring opening of benzyl 2-O-p-tosyl-3,4-anhydro-β-l-arabinopyranoside (1) or benzyl 2,3-anhydro-4-O-acetyl-α-d-ribopyranoside (3), respectively, using sodium acetate, sodium iodide, and acetic acid in acetone which on treatment with POCl3 in pyridine yielded the unsaturated sugars 6 and 7. After deacetylation of 7 with MeOH/H2O/Et3N (3:2:1) and treatment of 8 with tosyl chloride/pyridine at 50 °C 9 was obtained. The reaction of benzyl 2-O-p-tosyl-3,4-dideoxy-α-d-glycero-pent-3-enopyranoside (6) and benzyl 2,3,4-trideoxy-4-chloro-β-l-glycero-pent-2-enopyranoside (9) with the sodium enolate of dimethyl propargylmalonate in the presence of catalytic amounts of tetrakis(triphenylphosphine)palladium(0) afforded the branched-chain sugars 10 and 11. The isomer 10 was obtained as a minor product from 6 with retention of configuration around C-2, and the major isomer 11 as a result of allylic rearrangement in a ratio of 1:9. On the other hand, compound 9 afforded 10 as a major product and its regioisomer 11 as a minor product in a ratio of 8:2; formation of the above mentioned isomeric mixture involves cis and trans diastereomeric intermediates during the reaction. Treatment of these precursors with Co2(CO)8 in benzene followed by oxidative decomplexation with DMSO yielded in a stereoselective manner the polysubstituted bis-cyclopentanoids 12 and 13. The stereochemistry of 13 was assigned with the help of X-ray analysis. Attempts were made to prepare the tetracyclic systems 15 and 17 using 12 and 13 with 3-acetoxy-2-[(trimethylsilyl)methyl]-1-propene (14); however, the alkylation products 16 and 18 were obtained.