A unified synthetic strategy: Synthesis of 11-deoxy PGE(2) and milbemycin alpha(1)

The use of dihydrofuran (1) as a chiral template for (2+2) -photocycloaddition is described. Photochemical cycloaddition of dihydrofuran 1 with cyclopentenone 2 provides synthetic entry into 11-deoxy PGE$\sb2$. While photocycloaddition between dihydrofuran 1 and cyclobutene 4 provides synthetic entry into the southern hemisphere of milbemycin $\alpha\sb1$. The synthesis of 11-deoxy PGE$\sb2$ is described in Chapter I. Cleavage of the corresponding diol of 3 followed by cyclobutane fragmentation provides aldehyde 11. This aldehyde is subsequently transformed into the target molecule 12.(DIAGRAM, TABLE OR GRAPHIC OMITTED...PLEASE SEE DAI) The synthesis of the oxahydrindane ring system of milbemycin $\alpha\sb1$ is described in Chapter II. The photoadduct 6 provided the ketone 7 by deoxygenation at C(8a) and oxidation at C(7). The two-carbon chain originating at C(8) was installed in a stercontrolled fashion using a (3,3) -sigmatropic rearrangement. Finally, late stage introduction of the trisubstituted olefin would provide the desired target 9.(DIAGRAM, TABLE OR GRAPHIC OMITTED...PLEASE SEE DAI)(Abstract shortened with permission of author.