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Solution and Solid Phase Synthesis of Unusual a-Amino Acids From

Solution and Solid Phase Synthesis of Unusual a-Amino Acids From

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synthesis (Scheme 3.3, left side) from acrolein 3.16 or in 6.6% yield by bromine<br />

displacement from ethyl-2-bromo-3-butenoate 3.17 (Scheme 3 -3, nght path). D-<br />

Vinylglycine was then obtained in approximately 82% ee by resolution with baker's<br />

yeadg<br />

Scheme 3.3<br />

2) cation exchange kn2 3) cation<br />

exchange<br />

Br<br />

3.1 6 3.7 3.17<br />

Racemic vinylglycine was also reportedly synthesized in 50% yield from 2-<br />

hydroxy-3-butenoic acid,"' however, no synthetic details were provided. In 1977,<br />

Baldwin et aL used the same 2-hydroxy-3-butenoic acid 3.18 to synthesize racemic<br />

vinylglycine in 26% overall yield (Scheme 3.4)?<br />

Scheme 3.4<br />

A better yield (48% for 3 steps) was achieved in 198 1 by f3-elimination <strong>of</strong> a silyl<br />

protected glycine enolate adduct 3.20 in a Petenon-type olefination (Scheme 3 S)."<br />

Scheme 3.5

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