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Atml. Calcd for C2~H26N4Na01~PS.3Hz0: P, 4.85; S, 5.02. Found: P, 4.84; S, 4.97. Preparation of 23. A solution of 13 (70 mg, barium salt) and the iodonucleoside 21 (340 mg) in 50% aqueous pyridine (3 ml) was heated at 70" for 7 hr. The purification procedure as described for 22 was used to obtain 60 mg (85%) of 23; X",' d: 267 mp ( E 17,880). Anal. Calcd for CZOH2BN4Na011PS: C, 41.08; H, 4.48; S, 5.48. Found: C, 40.94; H, 5.27; S, 5.29.Treatment of 3 with Aqueous Iodine. A solution of 3 (50 mg) in 50% aqueous acetone (2 mi) was treated with iodine (100 mg) for 17 hr, and then diluted with water (10 ml) and extracted with ether (three 5-ml portions). The residual ether was removed from the aqueous layer by evaporation, and the solution was applied to a 195 DEAE column (50 X 2.3 cm, acetate form) which was eluted with a gradient of 2 1. of acetate buffer, pH 6 (0.005 M ) in the mixing vessel. and 2 1. of the same buffer (0.2 M ) in the reservoir. 3'-0-Acetylthymidine 5'-phosphate, 731 ODzs7 units (77%;) was eluted from the column in fractions 72-83, and was identified by comparison with an authentic sample.23Acknowledgments. Thanks are extended to Dr. V.Abstract: A dodecapeptide amide with the structure proposed by Mutt and Jorpes for the C-terminal sequence of the intestinal hormone cholecystokinin-pancreozymin has been synthesized by the condensation of three fr!gments: di-, tetra-, and hexapeptide. All the fragments were prepared by the stepwise procedure using active esters, and the coupling of the intermediate peptides was carried out by the azide method. The synthetic dodecapeptide (XX) was identical with the natural counterpart isolated by partial tryptic digestion of the hormone. This C-terminal sequence has all the biological properties of cholecystokinin-pancreozymin.n 1928 Ivy and Oldberg' proposed the name chole-

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