Über die Synthese von 2-(p-Biphenylyl)-isopropyloxycarbonyl-(Bpoc)-Aminosäuren und den Zerfall von Aralkyl-phenyl-carbonaten

The syntheses of a number of new Bpoc-amino acids and the preparation of some activated esters of Bpoc-amino acids are described. In recent work on the total synthesis of calcitonin hormones the Bpoc residue has been found to be very useful for the selective protection of α-amino groups of complicated intermediate peptide fragments. The reagent preferentially used for the introduction of the Bpoc group into amino acids, 2-(p-biphenylyl)-isopropyl]-phenyl-carbonate (I), is stable at 0°, but undergoes at higher temperatures a decomposition which is a accelerated by phenol. Based on the reaction products formed — 2-(p-biphenylyl)-isopropyl]-phenyl-ether (II), 2-(p-biphenylyl)-propene (III), and phenol — a scheme is proposed for this thermal decomposition, and the possibility of a correlation between the stability of carbonates R₃C—O—CO—OC₆H₅ and the rate of the acidolytic cleavage of urethanes R₃C—O—CO—NHR′ depending on the substituents R is discussed.