4 N-ACYLBENZOTRIAZOLES: NEUTRAL ACYLATING REAGENTS FOR
 THE PREPARATION OF PRIMARY, SECONDARY AND TERTIARY
 A M ID E S ........................................................... ................ 5 2

 4.1 Introduction ............... .... .................... ..........................52
 4.2 R results and D discussion ................................................................................. 53
 4.2.1 Preparation of N-Acylbenzotriazoles 4.2a-q........................ .................53
 4.2.2 Preparation of Primary Amides 4.3a-n from N-Acylbenzotriazoles
 4.2 w ith A m m onia. ................ ... .. ... .. ..... .. .. .. .... .................... 55
 4.2.3 Preparation of Secondary Amides 4.4a-j from N-Acylbenzotriazoles 4.2
 w ith Prim ary A m ines .................................................................... ... 56
 4.2.4 Preparation of Tertiary Amides 5a-k from N-Acylbenzotriazoles 4.2
 w ith Secondary Am ines. ....................... ................ .... ............... 57
 4.2.5 Preparation of a-Hydroxyamides using BtSO2CH3. ...............................58
 4.2.6 Preparation of 1-(1H-1,2,3-Benzotriazol-l-yl)-2,2,3,3,4,4,4-
 heptafluorobutan-1-one (4.8) and its Perfluoroacylation with Primary and
 Secondary A m ines. .......................... ........ ........................... ...... ............59
 4.3 Conclusion .................................................................... ......... 61
 4.4 E xperim mental Section ............................. ................................................... 61
 4.4.1 Modified procedure for the Preparation ofN-(1-
 m ethanesulfonyl)benzotriazole (4.1) ....................................... ............... .... 61
 4.4.2 General procedure for the Preparation of N-Acylbenzotriazoles 4.2........62
 4.4.3 General procedure for the Reaction of N-Acylbenzotriazoles 4.2 with
 A queous am m onia. ................... ...................... .... ........ .. ....... ............ 65
 4.4.4 General procedure for the Reaction of N-Acylbenzotriazoles 4.2 with
 P rim ary am ines. .................... ...... ......... ... ............................... ... 65
 4.4.5 General procedure for the Reaction of N-Acylbenzotriazoles 4.2 with
 Secondary am ines. ..................... .... ....... .. ...... ........ .........................67
 4.4.6 General procedure for the Preparation of a-Hydroxyamides.....................68
 4.4.7 Preparation of 1-(1H-1,2,3-Benzotriazol-l-yl)-2,2,3,3,4,4,4-
 heptafluorobutan-1-one (4.8) ..................................................... .................69
 4.4.8 General Procedure for the Reaction 4.8 with Primary and Secondary
 am in es. ....................................................... ................ 6 9

5 HIGHLY DIASTEREOSELECTIVE PEPTIDE CHAIN EXTENSIONS OF
 UNPROTECTED AMINO ACIDS WITH N-(Z-a-AMINOACYL)
 B E N Z O T R IA Z O L E S ........................................................................ ...................7 1

 5.1 Introduction .................................. ..............................................7 1
 5.2 R results and D discussion .................. .... ... .............................. ............... 73
 5.2.1 Preparation of N-(Z-Aminoacyl)benzotriazoles from N-Cbz-Amino
 a c id s 5 .1 a d .................................................... ................ 7 3
 5.2.2 Preparation of N-Z-Dipeptides ..................................................................75
 5.2.3 Preparation of N-Acylbenzotriazoles derived from N-Z-Dipeptides..........76
 5.2.4 Preparation of N-Z-Tripeptides. ........................... ............... 77
 5.2.5 Preparation of N-Z-Tetrapeptides.............. ..............................................78