3- Azabicyclo 3.3,1 nonene synthesis

Bolton, G. L. Solid Phase Synthesis of Azabicyclo[4.3.0]nonen-8-one Amino Acid Derivatives via Intramolecular Pauson-Khand Cyclisation, Tetrahedron Lett. 1996, 37, 3433—3436. 

Several routes to cycloalkanes have been developed (Fig. 4). Bolton [29] described the synthesis of azabicyclo[4.3, 0]nonen-8-ones using an intramolecular Pauson-Khand cycliza-tion. The relative stereochemistry was controlled in this cyclization step which proceeded in good yield regardless of whether the nitrogen atom bore an allyl (shown) or propargyl (not shown) substituent. The ene reaction was employed in a route to trans-substituted cyclopentane and cyclohexanes [30], Reductive cleavage from the resin with LiBFL, provided the diol or, alternatively, cleavage with Ti(OEt)4 produced the diester. 

Tomita T, Kita Y, Kitamura T, Sato Y, Mori M (2006) Further studies on enantioselective synthesis of (-l-)-anatoxin-a using en5oie metathesis unexpected inversion of chirality via a skeletal rearrangement of 9-azabicyclo[4.2.1]nonene derivative. Tetrahedron 62 10518-10527. doi 10.1016/j.tet.2006.05.088... 

The total synthesis of (-l-)-anatoxin-a was achieved by Martin et al. 12a, b and Mori et al. [12c, d] by using the same strategy. The key step is the constraction of an azabicyclo[4.2.1]nonene ring system. For that purpose, the 2,5-ds-disubstituted pyrrolidine derivative 34 was synthesized from (-l-)-pyroglutamic acid. Ene-yne metathesis appHed to 34 was carried out using second-generation catalyst [Ruj-II to form the azabicychc compound 35 [12a, b], which was chemoselectively dihy-droxylated to provide 36. From the latter compormd, anatoxin-a was synthesized (Scheme 6.9). 

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