Diastereoselective synthesis of 2-alkylated 4-silyloxyproline esters

…, S Yagi, SAA El Bialy, J Uenishi, M Yamauchi…

Index: Sato; Kawasaki; Oda; Yagi; El Bialy; Uenishi; Yamauchi; Ikeda Journal of the Chemical Society. Perkin Transactions 1, 2001 , # 20 p. 2623 - 2631

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Abstract

Treatment of the 4-silyloxy-N-Boc-L-proline methyl ester 1 with allyl bromide in the presence of LDA in THF at− 78° C gives a mixture of the (2S, 4R)-and (2R, 4R)-2-(prop-2-enyl)-4- silyloxy-N-Boc-L-proline esters 2a and 2b in 75% combined yield in the ratio 53∶ 47. In contrast, similar treatment of the (−)-and (+)-menthyl esters 5 and 6 gives a mixture of allylated products 7a, b and 8a, b in the ratio 75∶ 25 and 89∶ 11, respectively. Reaction ...