Rink amino methyl resin

In a first report, Sohma and coworkers [72] synthesized the highly hydrophobic peptide Ac-Val-Val-Pns-Val-Val-NH2 (Pns, phenylnorstatine) on a Rink amino methyl resin and obtained only a 6.9% yield after purification. Analysis of side products indicated incomplete Fmoc deprotection and incomplete acetylation arising from aggregation. In contrast, when the branched ester was constructed on the same resin and then converted into the parent peptide in phosphate-buffered saline (PBS) at pH 7.4, the yield increased to 54%, although a small amount of racemized product (3.2%) was observed. Similar results were obtained when using Ser in the place of Pns. 

Resin deprotection Rink amide resin [4-(2 ,4 -dimethoxyphenyl-Fmoc-amino-methyl) phenoxy resin] with a loading of approximately 450pmolg was subjected to repeated washes with 20% piperidine/DMA until no UV absorption due to cleaved dibenzofulvene derivatives was detected in the el-uate. 

Perfluoro(3-isothiocyanato-2-methyl-2-pentene) reacts with N-nucleophiles to produce a series of fluoroalkyl-substituted 6/f-l,3-thiazines <1997RJO720>. The acid-catalyzed cyclization of thioureas immobilized on Wang (X = O) or Rink resin (X = NH) provides a convenient route to a wide range of 2-amino-4/7-benzothiazine derivatives 212 (Scheme 23) <20000L3667>. The thioureas are obtained in four steps from 2-nitrocinnamic acids. A general synthesis of 2-alkylidene-4-imino-l,4-dihydrobenzo-l,3-thiazines 213-215 involves treatment of 2-isothiocyanato-benzonitrile with acidic methylene compounds under basic conditions <2003SL1503>. The ( )-isomers are the predominant isomers formed. 

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