Formal Total Synthesis of (+/-)-α- and β- Cedrene by Preparation of Cedrone. Construction of the Tricyclic Carbon Skeleton by the Use of a Highly Efficient Intramolecular Khand Annulation William J. Kerr,* Mark McLaughlin, Angus J. Morrison, and Peter L. Pauson

William J. Kerr University of Strathclyde – Glasgow U.K. B.S University of Strathclyde Ph.D University of Strathclyde – Peter Pauson and David Billington NIH Postdoc – Brandeis University - MA – Myron Rosenblum Postdoc – Imperial College – London – Steven Ley 1989 – University of Strathclyde – 1991 – ICI Fine Chemicals Young Lecturer – 1997 Glaxo Welcome Prize for Innovative Organic Chem – 2002 Chair of Organic Chemistry – University of Strathclyde Interests: Metal Mediated Synthetic Organic Chemistry

α- and β-Cedrene Isolated in 1841 – Walter, P. Ann. Chem. 1841, 39, 247 – Juniperus cedrus and Juniperus thurifera Characterized in 1953 – Stork, G.; Breslow, R. J. Am. Chem. Soc. 1953, 75, 3291

Retrosynthesis Key Step: Intramolecular Pauson Khand Pauson Khand cyclization has been used in synthesis of other natural products. – Pentalenene, Hirsutene, Brefeldin A…etc

Forward Synthesis Scheme 1 2 nd Step: Originally - Saegusa Oxidation – Worked 92% yield Not Catalytic – Used diallyl carbonate stoichiometric

Scheme 2 Seyferth-Gilbert Homologation – Ohira-Bestmann reagent

Scheme 3 Pauson-Khand Cyclization

Scheme 4 Mech of ketone deprotection

Final Steps Scheme 5.

Conclusion Able to utilize the Pauson Khand cyclization – Formation of intermediate Synthesis of target from simple starting material Questions??