A sequential procedure has been developed whereby neutral amino acids 1 were tritylated via their corresponding trimethylsilyl esters 2 to afford, after mild hydrolysis, IV-trityl amino acids 3 in high yields and purity. Hydroxy amino acids 4 were preferentially tritylated at the amino function by using either Me3SiCl or Me^iCtj (or Ph^iCy for temporary protection of the hydroxy and carboxyl groups. Finally, !Vim-tritylhistidine (9c) was prepared in 97% yield with the aid of the Me2SiCl2, whereas the use of Me3SiCl produced, after tritylation, IV"-tritylhistidine (9b) and 9c in almost equimolar amounts.It is well-known that the trityl moiety as an a-amino protecting group in peptide synthesis can be selectively removed, under extremely mild acidic conditions2, in the presence of other acid-sensitive protecting group.3 In addition, racemization during the coupling step using IV-trityl amino acids is expected to be lower in comparison to otherwise N-protected amino acids.However, the application of the trityl function in peptide synthesis is limited because of the low yields in the prep-aration2,4 of IV-trityl amino acids and their failure, with a few exceptions,2 to couple with other amino acids in acceptable yields.2 While the latter obstacle has been overcome, when dicyclohexylcarbodiimide, mediated with 1-hydroxybenzotriazole, was used as the coupling agent,5 the facile preparation of IV-trityl amino acids remains to be a serious problem.The present synthesis readily provides IV-trityl amino acids in high yields by an experimentally simple "one-pot" procedure involving tritylation of silylated esters of amino acids followed by mild cleavage of the susceptible oxygen-silicon bond.

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Application of 4-Polystyryltriphenylmethyl Chloride to the Syntheses of Peptides and Amino Acid Derivatives Use of polymcr-bound ttityl chloride as an a-amino protccting group of amino acids allows sirnplc and high-yicld synthcscs of amino acid dcrivativcs and pcptides.Polymere Gruppen sind wegen ihrer komplizierten Regenerierbarkeit nur wenig zum Schutz von Amino-Funktionen wahrend der Darstellung von Aminosaure-Derivaten und Peptiden eingesetzt worden 'I. Wir verwendeten deshalb das leicht regenerierbare, durch Polystyrol (als 1,4-Divinylbenzol-Copolymerisat) substituierte*) Tritylchlorid 2 zur Darstellung von 4-Polystyryltriphenylmethylaminosauren 3 und deren Derivate.So erhalt man 3, analog3) zur Darstellung von Tritylaminosauren 11, durch Reaktion von 2 rnit Aminosaure-trimethylsilylestern (im UberschuR) in Chloroform. Die resultierenden Aminosaure-substituierten Harze 3 sind rnit 0.90-1.05 mmol Aminosaure je g Harz beladen, entsprechend einer iiber 92proz. Umsetzung mit Ausnahme von 3b (68proz. Umsetzung). Durch Reaktion rnit 1-Hydroxybenzotriazol und Dicyclohexylcarbodiimid werden die Verbindungen 3 in die Aktiv-Ester 4 ubergefiihrt. Wie man aus der Abwesenheit der typischen4) Amid-IR-Absorptionsbande bei 1740 cm-' erkennt, werden die Verbindungen 4, anders als die entsprechenden Tritylaminosaure-

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N‐Tritylaminosäure‐(1‐benzotriazolylester) 1 werden bei 30–80°C in Gegenwart von überschüssigem Triethylamin racemisierungsfrei an Amino‐Komponenten gekuppelt.