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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

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

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CbzH<br />

6.23<br />

OTs<br />

238<br />

Nal, DMF<br />

6.24 6.25<br />

In order to attach the amino acids 6.26 <strong>and</strong> 6.27 ont0 the min via their N-tennini,<br />

conversion <strong>of</strong> the methylene hydroxyi moiety in both Wang (0.74 mrnoVg loading) <strong>and</strong><br />

TentaGel PHBQ (0.30 mmoVg loading) resins into a carbarnate linker was necessary. The<br />

resins were activated as either the imidazolide carbarnate 630 using NN-<br />

carbonyIdiimidazo1e 628 in THF or the p-nitrophenol carbonate 6.31 using p-<br />

nitrophenolchlor<strong>of</strong>ormate 6.29 <strong>and</strong> N-methyl morpholine 0 in CH2C12 (Scheme<br />

6.1 1 ). Loading was monitored by elemental analysis for nitrogen <strong>and</strong> was generally<br />

quantitative for both carbonyldiimidazole 6.28 <strong>and</strong> p-nitrophenoichlor<strong>of</strong>ormate 6.29 (see<br />

Appendix E for calculation) on both Wang <strong>and</strong> TentaGel PHBa resin. The imidazolide<br />

<strong>and</strong> carbonate resins were both stable for six months without loss <strong>of</strong> activity.

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