Route Selection for Cyclopentenone

4) Optimization of the assembly of 2, 3, and D-valine to finish the preparation of our target 1 (end game). 

We will discuss each topic below. Later, we will discuss the key reaction, asymmetric nucleophilic addition of a n-allyl Mo complex, in great detail. 

Although cyclopentanone 2 is a rather simple looking small molecule, the 3,4-trans-substituted architecture in a cyclopentanone ring provides significant complexity to this molecule. We devised two alternative routes for the preparation of 2. 

2 Asymmetric Nucleophilic Addition of a ir-Allyl Mo Complex route 

The chiral center would be installed from either Unear carbamate 15 or branched carbamate 16 via the asymmetric addition of malonate anion to the 7i-allyl Mo complex reported by Trost et al. [11] to afford the branched chiral malonate derivative 17. Decarboxylation of 17 should provide the mono-carboxylic acid 18. Masa-mune homologation with 18 affords our common precursor 14. Linear carbamate 15 was obtained from the corresponding cinnamic acid, and branched 16 was prepared in one pot from the corresponding aldehyde. 

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