Figure 1: Rationale for stereoselective assembly of the indolizidine core using chiral allylsilanes. Jump to Scheme 5 Finally, we examined the behaviour of alcohol 12 under cross-metathesis conditions. Larry Yet. Further, the use of chiral allylsilanes as cross-metathesis partners would potentially facilitate an asymmetric approach to the total synthesis of 1.
This, in turn, was prepared in four steps by alkylation of an acetylide anion with commercially available iodomethyltrimethylsilane, followed by partial reduction of the alkyne.
Naga Siva Rao, R. Scheme 3: Completion of the total synthesis of tashiromine 1. The absolute stereochemistry of the newly established asymmetric centres would be controlled by allylic strain arguments, assuming that the well-established precedent for anti-SE2' attack of the iminium on the allylsilane was upheld here. Bande, Vedavati G. Kalamkar, Vijay M. Figure 1: Rationale for stereoselective assembly of the indolizidine core using chiral allylsilanes.
Background Tashiromine 1 is a naturally occurring indolizidine, isolated from an Asian deciduous shrub Maackia tashiroi. The boronic acid Mannich reaction in alkaloid synthesis. The Journal of Organic Chemistry , 76 9 , Larry Yet. European Journal of Organic Chemistry , 9 , Further, the use of chiral allylsilanes as cross-metathesis partners would potentially facilitate an asymmetric approach to the total synthesis of 1.
Puranik, Dilip D. Scheme 2: Stereoselective construction of the indolizidine core 2. Kasture and Dilip D. Additionally, the spectral data for the diastereomeric epi-tashiromine have been reported and differ significantly from those recorded for 1 . Abstract Background Tashiromine 1 is a naturally occurring indolizidine alkaloid. Tetrahedron Letters , 52 7 ,
Schmidt, S. Specifically, we envisaged that cyclisation precursors of type 9 ought to be readily available by cross-metathesis of 5 with an appropriate chiral allylsilane followed by chemoselective partial reduction by borohydride. Joseph P. Our own approach  utilises an intramolecular addition of an allylsilane to an N-acyliminium ion to deliver the [4. Jadhav, Vedavati G. We report herein full details of the successful synthesis of racemic tashiromine 1 by this strategy  , as well as our initial attempts towards an asymmetric variant.
Tetrahedron Letters , 52 7 ,
Pyne, Andrew S. Thunwadee Ritthiwigrom and Stephen G. Chopade, Dilip D. Thus, the predicted major stereoisomer 10 would have 5S,6S stereochemistry and an E-configured side-chain, while cyclisation to the predicted minor 5R,6R isomer 11 would be disfavoured by A1,3-interactions between the R1 group and vinylic proton leading to the Z-configured side-chain.
Full experimental details and compound characterisation data for all new compounds described. Further, the use of chiral allylsilanes as cross-metathesis partners would potentially facilitate an asymmetric approach to the total synthesis of 1. Win-Mason, Gregory W.