Acetic acid, trimethylsilylethyl ester

Amino acid coupling of 1257 with 1252 (R = CH2CH2Si(CH3)3) was accomplished using DCC/DMAP to afford 1258 (Scheme 1.321). Sequential deprotection of the phthalimide and (3-trimethylsilylethyl ester was straightforward. Macrolac-tamization of the resulting amino acid and hydrolysis of the dioxane moiety completed the synthesis of 1183. The authors observed a small amount (8-10%) of double bond isomer, but showed that this resulted from hydrolysis of the mesitylene acetal. 

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