Attwntion is callod for a supwrb stratwgy of pwptido SYnthW8iS in solution, making usw of (pwr)silylatwd amino acid fraqmwnts. This old mothodology m a y thus prwrwnt rwnwwwd intwrwst if thw classical silylation is substitutod by silyl cyanidws during coupling. Thus, trimwthylsilyl cyanidw, by its pronouncwd silylating powor affording only gaswous following-(by)products and by its wxcwllwnt solubiliring propwrtiws in organic solvwnts, ovorcomws tho difficultiws and drawbacks that w w r w oncountwrwd in proviously dwscribwd strrtwgiws that mad. Us.of w xtwmporw prWp8r.d (pwr)silylatod amino acid rwsiduws.Silylation is a uwll known procwdurw ( 1 . 2 ) which finds innumwrablo applications in gas chromatography (3). mass spwctromwtry (4). during tho incorporation of polymwric mpacwrs, tho idwntification studios of s u g a r s WtC.. and last but not l W 8 . t in many synthwsws and a 8 blocking groupingc nwodwd 0.9. during thw prwparation of usofull synthons ( 5 ) . A panoply of procwdurws and silylation rwagonts wnist ( 1 . 2 ) and thw subjwct is on. of thw most olaboratod and dwscribwd among thosw rwlatwd with protwction and masking of ChWmiC8l functionalitiws posswssing activw hydrogon atoms on nucloophilic sitws. AdVantagWS in thw usw of N,O-(pwr)silylatWd amino acids in pwptidw synthwsis havw since long bwon rwcognizwd sincw thw pionowring work of Birkofwr wt a1. and of Krichwldorf ( 6 ) . -____-_-_________ *Thw publication of this m.s. has bwwn dwlaywd on wnplicit roquwst of thw authors. -119 -Tho oxcollont yiolds in coupling silylatod amino compononts accompaniod by low racrmizations arm noticoablo. Some disadvantagos by using moro clas8ical silylation roagonts howovor havo novor sinco boon fully circumvmntod, a1 though major succo8sos hAV, boon obtained with lHS-Cl/Et3N in rofluxing CH2C12 (6.). Still. uncomploto silylation rosults in a loss o f silylatod compononts and difficulties in dosagos and soparation. rrsulting in a nmod f o r an input o f mxcoss o f silylatod coreactants. Furthormoro, mxtra nucloophilic functions can somotimms hardly bo silylatod and romain ofton unprotoctrd thus loading to unwantod sido-roactions and docroasod yields. Othor major disadvantages would bet ( i ) a nood for water-fro0 roagonts and solvwnts and ospocial-so-obtained from dipmptidmaftmr frmmzm dryingis trmatmd with mxcmss TtlS-CN as thm rmagwnt and solvmnt. T h o addition o f a nmwly N-protmctmd carboxylic-activatmd componmnt, and thus rmpmating the coupling procmdurm, allows tho rapid mlongation o f tho pmptIdm chain. It is intermsting to note that o n trmatmmnt of pmptidic matorial with TtlS-CN, and at variancm for frmm amino acids during thm first stmp of dipmptidm-formation. hmating is not a prmrmquisitm for rapid dmrivatization. Thim fact is important in ordmr to surprmss totaly (intramolmcular) cyclic pmptidic matmrial. tion without PurificatLpn o f i n t e r m --. A . P-tion o f Z ----Glv Phm Smr w. 1.1 mmol (116 mg) o f powdmrrd Smr-OH is "dissolvmd" (5 min.) at 60-80mC in 1 ml TtlS-CN and to this, a solution o f 1 m...
