Synthesis strategic bond approach

In principle, several approaches to the complex tricyclo[5-3-l 0 ] undecane skeleton of seychellene can be devised by strategic bond disconnection. The synthesis by Piers et al. illustrates one of these approaches involving the base-catalyzed intramolecular cyclization of a suitably functionalized c/s-decalone (B) to norseychellanone. 

Smith and co-workers reported their second-generation approach to discodermolide in 1999, which was now performed in the correct enantiomeric series [46—48]. By carefully redesigning the route, the overall number of steps was significantly reduced and, importantly, it enabled a gram-scale synthesis. As outlined in Scheme 7, the key bond constructions at C8-C9 and C14-05 were retained, while strategic modifications involved the earlier introduction of the terminal (Z)-diene unit in 44 and a revised C1-C8 subunit 45. 

The Mn mediated radical additions offer an inherently flexible carbon carbon bond construction approach to amine synthesis. Because of the broad functional group compatibility in both the radical precursor and the aldehyde hydrazone acceptor, the roles of these precursors can be switched to result in the construction of either of two C C bonds at the chiral amine (Scheme 2.10) with excellent stereocontrol. The epimeric configuration can be selected by either (a) employing the enantiomeric auxiliary or (b) interchanging the roles of R and in the alkyl halide and aldehyde precursors [47]. By combining these two tactics, the optimal roles of R and with respect to yield and selectivity can be chosen. Such strategic flexibility contributes to the synthetic potential of these radical addition reactions. 

Both results point to the very low tendency of these Pt(II) centers to form Pt Pt bonds by this procedure. However, as chemistry is an experimental science, other strategic approaches can be used for the synthesis of polynuclear complexes with Pt Pt bonds (Scheme 6), " but that will be another story. 

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