Metal-Mediated Synthesis of Medium-Sized Rings

Carbon−Carbon Bond Formations Involving Organochromium(III) Reagents

An intramolecular Heck reaction (90 → 91) serves as the key step in the total synthesis of the titled compounds. The synthetic route is based on utilizing the Wieland−Miescher ketone (5) as a matrix to provide the C and D rings of the targets and to provide functionality implements for joining this sector to an A ring precursor (6). Catalytically induced enantiotopic control and early emplacement of the oxetane are other features of the route.

Total Synthesis of Baccatin III and Taxol

Progress in the construction of cyclooctanoid systems: new approaches and applications to natural product syntheses.

Five synthetic approaches to racemic strychnine (1), with the cobalt-mediated [2 + 2 + 2] cycloaddition of alkynes to indoles as the key step, are described. These include the generation and attempted cyclization of macrocycle 8 and the synthesis of dihydrocarbazoles 15, 22, and 26 and their elaboration to pentacyclic structures via a conjugate addition, dipolar cycloaddition, and propellane-to-spirofused skeletal rearrangement, respectively. Finally, the successful total synthesis of 1 is discussed. The development of a short, highly convergent route (14 steps in the longest linear sequence) is highlighted by the cyclization of enynoylindole 40 with acetylene and the formal intramolecular 1,8-conjugate addition of amine 49 to form pentacycle 50. Numerous attempts toward the formation of the piperidine ring of 1 from vinyl iodide 56 were made and its successful formation via palladium-, nickel-, and radical-mediated processes is described.

Approaches to the Synthesis of (±)-Strychnine via the Cobalt-Mediated [2 + 2 + 2] Cycloaddition: Rapid Assembly of a Classic Framework

Synthetic studies toward the taxane class of natural products

Investigations of the intramolecular Ni(II)/Cr(II)-mediated coupling reaction: Application to the taxane ring system

A concise synthesis of enantiomerically pure taxane C-ring via the [2,3] wittig rearrangement

Novel syntheses of β-halo-α,β-unsaturated ketones

The tricyclic enone 12, containing the taxane ring system, has been synthesized, using an intramolecular Ni(II)/Cr(II)-mediated coupling of β-iodoenone aldehyde 11 as the key step.

Michael H. Kress

Papers

Synthetic studies toward the taxane class of natural products

Investigations of the intramolecular Ni(II)/Cr(II)-mediated coupling reaction: Application to the taxane ring system

A concise synthesis of enantiomerically pure taxane C-ring via the [2,3] wittig rearrangement

Novel syntheses of β-halo-α,β-unsaturated ketones

Synthetic Studies Toward the Taxane Class of Natural Products.