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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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6.3 in 61-88% yield <strong>and</strong> purities <strong>of</strong> 70-95% (Scheme 6.2).19 This methodology was later<br />

exp<strong>and</strong>ed by using chiral phase transfer cataiysts to synthesize simple glutarnic acid<br />

Scheme 6.2<br />

BEMP<br />

6.1 1)HCWF ,<br />

4) TFA<br />

z z z<br />

6.3<br />

R',R~~R~=CO&~~, Me, Ph<br />

Z=C02Me, CN, S02Ph<br />

The recognized therapeutic properties <strong>of</strong> dehydroamino acids 6.62' <strong>and</strong> their<br />

incorporation in peptide libraries have ken addressed by the DBU catalyzed elimination<br />

<strong>of</strong> the sulfone 6.5 generated by oxidation <strong>of</strong> the derivatized cysteine 6.4 attached to the<br />

resin via the sidechain (Scheme 6.3). The dehydro-peptides 6.6 were generated in 3 1-<br />

86% yield over 4 steps <strong>and</strong> generally >!XI% purity. Cycloadditions have also been<br />

perfomed on the solid-phase on Fmoc-dehydroalanine generated through a sirnilar<br />

oxidation/elimination strategy in which cysteine is attached to the resin via the a-<br />

Scheme 63<br />

Fll=Boc. Cbz, Cbz-Phe, 1-Nap<br />

#=OM~, OBn, NHBn. PheOEt

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