Diastereoselective synthesis of 2-alkylated 4-silyloxyproline esters

Treatment of the 4-silyloxy-N-Boc-L-proline methyl ester 1 with allyl bromide in the presence of LDA in THF at, -78 degreesC 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 treatmen...

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Published inPerkin 1 : an international journal of organic and bio-organic chemistry no. 20; pp. 2623 - 2631
Main Authors Sato, T, Kawasaki, S, Oda, N, Yagi, S, El Bialy, SAA, Uenishi, J, Yamauchi, M, Ikeda, M
Format Journal Article
LanguageEnglish
Published CAMBRIDGE Royal Soc Chemistry 11.10.2001
Subjects
Chemistry
Chemistry, Organic
Physical Sciences
Science & Technology
DESIGN
ASYMMETRIC-SYNTHESIS
(-)-CEPHALOTAXINE
MIMETICS
PEPTIDES
ALPHA-ALKYLPROLINE DERIVATIVES
ACIDS
ALKYLATION
FORMAL TOTAL SYNTHESIS
METHYLPROLINE
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Summary:Treatment of the 4-silyloxy-N-Boc-L-proline methyl ester 1 with allyl bromide in the presence of LDA in THF at, -78 degreesC 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 of 6 with methyl iodide and propyl iodide also give the corresponding 2-alkylated esters 16a and 16b in a highly diastereoselective manner (94:6 and 93:7, respectively).
ISSN:1472-7781
DOI:10.1039/b105238c