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Allylsilane‐Modified Amino Acids from the Claisen Rearrangement
Author(s) -
Mohamed Mustafa,
Brook Michael A.
Publication year - 2002
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.200290002
Subject(s) - chemistry , chlorosilane , claisen rearrangement , yield (engineering) , diastereomer , reagent , silylation , stereoselectivity , alkyl , medicinal chemistry , stereochemistry , silanes , organic chemistry , catalysis , silicon , materials science , silane , metallurgy
The Claisen rearrangement of the N ‐protected, silylated allyl glycinates 11 and 12 led to the formation of allyl/silyl‐functionalized amino acids 13 and 14 in yields up to 80%. The diastereoisomer ratio varied from 2 : 1 to 29 : 1 for 11mb , and from 2 : 1 to 46 : 1 ( syn / anti ) for 12mb , depending on reaction conditions, as shown by X‐ray crystallographic analysis of 14mb . The relationship between the size of the alkyl groups on the chlorosilane reagent (Me 2 R″SiCl, R″=Cl, Me, t ‐Bu, Ph) used as an enolate trap and the observed stereoselectivity was investigated in the case of the Ireland – Claisen variant. Me 3 SiCl gave the best results. However, the size of the alkyl groups on the silylated ester (Me 2 R″Si, R=Me, t ‐Bu, Ph, i‐Pr) did not exert a significant effect on the diastereoselectivity or yield of the rearrangement.