Ring-closing alkyne metathesis stereoselective synthesis

Eurstner, A. and Rumbo, A. (2000) Ring-closing alkyne metathesis. Stereoselective synthesis of the cytotoxic marine alkaloid motuporamine C. J. Org. Chem., 65,2608-2611. 

RCM of dienes to cycloalkenes provides a useful method for the syntheses of carbo- and heterocycles and thus has been proved to be extremely effective in total synthesis of various natural products. Usually, however, mixtures of (E)- and (Z)-olefms result. In contrast, ring-closing alkyne metathesis provides a reliable route for synthesis of both (E)- and (Z)-macrocycloalkenes in a stereoslective manner taking advantage of stereoselective partial reduction of resulting cycloalkynes. A Lindlar reduction gives (Z)-cycloalkenes, whereas a hydroboration/ protonation sequence afford ( )-cycloalkenes (Equation (23)). Recently, Trost reported an alternative procedure for the synthesis of (E)-olefins from alkynes through hydrosilylation by a ruthenium catalyst. This procedure converts cycloalkyne 130, for example, to vinylsilane 131 and then to (E)-cycloalkene 132 in a stereoselective manner (Scheme 46)7 ... 

Furstner, A., Guth, O., Rumbo, A., Seidel, G. Ring Closing Alkyne Metathesis. Comparative Investigation of Two Different Catalyst Systems and Application to the Stereoselective Synthesis of Olfactory Lactones, Azamacrolides, and the Macrocyclic Perimeter of the Marine Alkaloid Nakadomarin A. J. Am. Chem. Soc. 1999,121,11108-11113. 

Furstner, A., Grela, K. Ring-closing alkyne metathesis application to the stereoselective total synthesis of prostaglandin E2-1,15-lactone. Angew. Chem., Int. Ed. Engl. 2000, 39, 1234-1236. 

Fiirstner, A. et al. 1999. Ring closing alkyne metathesis. Comparative investigation of two different catalyst systems and application to the stereoselective synthesis of olfactory lactones, azamacro-lides, and the macrocyclic perimeter of the marine alkaloid nakadomarin A. J Am Chem Soc 121 11108. 

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