Asymmetric synthesis of new beta,beta-difluorinated cyclic quaternary alpha-amino acid derivatives.
Santos Fustero, María Sanchez-Roselló, Vanessa Rodrigo, Carlos del Pozo, Juan F Sanz-Cervera, Antonio Simón, Carmen Ramírez de Arellano
Index: Org. Lett. 8 , 4129, (2006)
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Abstract
The synthesis of new beta,beta-difluorinated cyclic quaternary alpha-amino acid derivatives 1 in which a ring-closing metathesis reaction (RCM) constitutes the key step is described. The approach employs imidoyl chlorides 3 as fluorinated building blocks, and the overall process involves the stereoselective creation of a quaternary stereocenter. Complete selectivity was achieved when (R)-phenylglycinol methyl ether was used as chiral auxiliary, allowing for the preparation of new six-membered cyclic fluorinated alpha-amino acids as single enantiomers.
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