An enantioselective synthetic method for alpha-alkylserines by the phase-transfer catalytic alkylation of 2-phenyl-2-oxazo-line-4-carbonylcamphorsultam (4a) was developed. The phase-transfer catalytic alpha-alkylation of 4a using P2-Et at -78 degrees C gave alpha-alkylation (75 similar to 99%, 90 similar to 97% de), which could be easily hydrolyzed to alpha-alkylserines.
An Efficient Strategy to Orthogonally Protected (<i>R</i>)- and (<i>S</i>)-α-Methyl(alkyl)serine-Containing Peptides via a Novel Azlactone/Oxazoline Interconversion Reaction
for the synthesis of (R)- and (S)-alpha-methyl(alkyl)serine-containing peptides is presented. Using (S)-phenylalanine cyclohexylamide 6 as chiral auxiliary, the optically pure azlactones (R)- and (S)-2 were synthesized via a novel azlactone/oxazoline interconversion reaction (Figures 3 and 6). These azlactones constitute fully protected and activated synthetic equivalents of (R)- and (S)-alpha-methylserine