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¡ï ¡ï ¡ï ¡ï ¡ï ¡ï ¡ï ¡ï ¡ï ¡ï ¡ï ¡ï ¡ï ¡ï ¡ï AnnF: ½ð±Ò+5, ·ÒëEPI+1, ¡ïÓаïÖú, ÐÁ¿àÁË 2013-01-13 10:44:50 sltmac: ½ð±Ò+10, »¶Ó³£À´±¾°æ½»Á÷ 2013-02-26 13:23:54
In order to establish whether the overall reaction from enan-tiomer pure N -Boc-phenylalanine leads to any loss of optical purity through partial racemization in presence of base,enantiomeric excess (ee) values of L-Ia and diastereoisomeric excess (de) values based on the stereoconfiguration of amino acid amide part of final product L-IIa obtained from L-N-Boc-phenylalanine were determined.
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While Boc-deprotected product (free amine) showed an ee of 99.4%, the target compound L-IIa arising through nucleophilic addition of L-Ia on a-phosphateisothiocyanate was obtained in 98.5% de.
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Thus, as expected, stereochemical configuration at a-carbon atom of the acid was practically unaffected and this synthetic transformation from chiral a-amino acid could be applied to a wide range of compounds without undergoing any significant loss of optical activity.
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Since both L-and D-isomers of N-Boc-phenylalanine are easily accessible, it provides a useful route to obtain both the enantiomeric forms of carboxamide Ia-c which are useful synthons to a variety of pharmaceuticals.
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The overall process for novel (L)/(D)- pseudo-peptide thioureas IIae-l is convenient, high yielding and atom-economic.
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