Efficient Synthesis of (<i>S</i>)-4-Phthalimido-1,3,4,5- tetrahydro-8-(2,6-dichlorobenzyloxy)-3-oxo-2<i>H</i>-2-benzazepin-2-acetic Acid (Pht-Hba(2,6-Cl<sub>2</sub>-Bn)-Gly-OH)<sup>1</sup>
作者:J. Richard Casimir、Dirk Tourwé、Koen Iterbeke、Gilles Guichard、Jean-Paul Briand
DOI:10.1021/jo000530d
日期:2000.10.1
4-Amino-2-benzazepin-3-ones have proven very useful for studying the biologically active conformations of peptides. The synthesis of Pht-Aba-Xaa-OH by reaction of the corresponding 1,3-oxazolidin-5-one with trifluoromethanesulfonic acid (TFMSA) has been reported in the literature. However, when this procedure was applied to the preparation of Pht-Hba(Bn)-Gly-OH 8, many byproducts were formed and the yield of the desired aminobenzazepinones 7 and 8 was very low. We report in this paper an efficient methodology for the synthesis of Pht-Hba(2,6-Cl-2-Bn)-Gly-OH 17 starting from the commercially available tyro sine. In our procedure, the dipeptide Pht-Tyr(2,6-Cl-2-Bn)-Gly-OH 15 is converted,to the 1,3-oxazolidin-5-one 16 Which then undergoes Friedel-Crafts cyclization in the presence of tin tetrachloride to afford the desired 4-phthalimido-1,3,4,5-tetrahydro-8-(2,6-dichlorobenzyloxy)-2-benzazepin-3-one 17 in excellent yield.