Diastereoselective ring closing metathesis

Scheme 9. Diastereoselective ring-closing metathesis and C8 methylation according to Kalesse et al. to synthesize C7-C2I (fragment A-B) (PMB = /i-methoxybenzyl).

Negishi E, Tan Z (2005) Diastereoselective, Enantioselective, and Regioselective Carbo-alumination Reactions Catalyzed by Zirconocene Derivatives. 8 139-176 Netherton M, Fu GC (2005)Pa]ladium-catalyzed Cross-Coupling Reactions of Unactivated Alkyl Electrophiles with Organometallic Compounds. 14 85-108 Nicolaou KC, King NP, He Y (1998) Ring-Closing Metathesis in the Synthesis of EpothUones and Polyether Natmal Products. 1 73-104 Nishiyama H (2004) Cyclopropanation with Ruthenium Catalysts. 11 81-92 Noels A, Demonceau A, Delaude L (2004) Ruthenium Promoted Catalysed Radical Processes toward Fine Chemistry. 11 155-171... 

Representatives of the bridged sulfone system 70 have been subjected to ruthenium catalysed ring-closing metathesis reactions (Grubbs catalyst) and shown to afford, in low yields, a few selected cyclic dimers and trimers, of all the possibilities available. The diastereoselectivities observed were rationalised in terms of kinetic control involved with internal ruthenium/sulfonyl oxygen coordination . 

Despite the unrivaled easy access to 1,4-dicarbonyl compounds, only a few examples of the application of Stetter reactions in the synthesis of natural products have been reported to date [55]. Tius et al. have employed a diastereoselective in-termolecular Stetter reaction and a ring-closing metathesis reaction as the key steps in their elegant synthesis of roseophilin (58 Scheme 9.16) [56]. The 1,4-... 

In a beautifully choreographed sequence of events, Judd and co-workers installed the C3 to C4 bridged bicyclic lactam moiety of 129 with diastereoselective control via an Ugi 4-component coupling, ring-closing metathesis, and Heck reaction <07OL5119>. 

Schmidt B, Westhus M (2000) Diastereoselectivity in a ring closing metathesis reaction with a remote stereogenic centre leading to quaternary dihydropyrans. Tetrahedron 56 2421-2426... 

Fustero, S., Bartolome, A., Sanz-Cervera, J. F., et al. (2003) Diastereoselective synthesis of fluorinated, seven-membered P-amino acid derivatives via ring-closing metathesis. Org. Lett., 5, 2523-2526. 

Polyfunctionalized pyrrolidines were diastereoselectively synthesized via ring-closing metathesis of 3-allyl-4-vinyl-2-oxazolidinones. Compound 202 gave the bicyclic system 203, converted into 204 through cis-dihydroxylation and oxazolidinone ring-opening <04SL49>. 

Fustero, S. Esteban, E. Sanz-Cervera, J.F. Jimenez, D. Mojarrad, F. An enantio- and diastereoselective synthesis of fluorinated beta-aminoalkyloxepine derivatives through Mannich and ring-closing metathesis reactions. Synthesis 2006, (23), 4087 1091. 

Jennings strategy for obtaining the macrolide skeleton was Yamaguchi esterification and ring closing metathesis (RCM) with 175 and 176 (Scheme 36). Construction of the key 2,6-cis-tetrahydropyran in 176 was carried out via diastereoselective axial reduction of an oxonium cation. The precursor, a pyranone, was prepared via RCM of divinyl ester 177. An asymmetric center was made by Brown s asymmetric allylation. 

Davies and co-workers also applied a ring-closing metathesis strategy in their preparation of constrained p-amino acid derivatives. Their work employed a chiral auxiliary, S -(l-phenyl-ethyl)-carbamic acid benzyl ester, to achieve the desired P-amino acid derivatives in a stereoselective fashion. Treatment of diene precursors 46 and 48 with 4 mol % of 3 in refluxing dichloromethane provided the corresponding carbocyclic P-amino acid derivatives 47 and 49 in 85 and 35% yield, respectively, with greater than 95% diastereoselectivity in both cases. The diminished yield in the case of 49 is presumably due to sterics effects. 

Heo, J. N. Micahzio, G. C Roush, W. R. 2003. Enantio- and diastereoselective synthesis of cyclic P-Hydroxy aHylsUanes via sequential aldehyde y-silylallylboration and ring-closing metathesis reactions,... 

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