【文章內(nèi)容簡介】 ester (ODmab) Similarly to Dde and ivDde, the Dmab protecting group can be removed with 2% hydrazine in DMF. O C H 2 C H C H 2 allyl ester (OAll) It can be removed in P(Ph)3 by Pd(0) catalysis. Succinimide ring formation (Asp): Acid catalised reaction results in a or bAsppeptides, however, piperidine catalised side reaction under Fmoc cleavage procedure results in piperidide: AspGly N H C H C O N H C H 2 C O C H 2 C O tBu O AsuGly N H C H N C H 2 C C O C H 2 O C O tBuOH N H C H C O N H C H 2 C O C H 2 C O N H C H C H 2 C C O O N C H 2 C O piperidine piperidine N N M = Mcalc+ 57 Application of other cleavage reagents (DBU, TBAF, DEA, morpholine) eliminate the piperidide formation, but not the succinimide formation. Addition of HOBt to the cleavage mixture can reduce the succinimide ring closure. But the best results may get with the use of Fmoc(Hmb) amino acid derivatives: Hmb: 2hydroxy4methoxybenzyl (removable with TFA) N H C H C O N C H 2 C O C H 2 C O tBu O (Hmb)amino acid derivatives are secundary amines: Removal of Fmoc group and the attachement of the next Asp derivative is difficult, needs longer time. Ninhydrin test can’t detect the efficacy of the coupling. Fmoc(FmocHmb)GlyOH 1g = 370 EUR (NovaBiochem) The increasing of the solubility of protected peptide fragments as well as preventing of aggregation of ”difficult” sequences can be reach by the application of Hmb groups. Side chain functional group protecting group name (abbreviation) wCONH2 (Asn, Gln) trityl (Trt) The solubility of FmocAsnOH and FmocGlnOH is extremely bad. The Trt protecting group increases the solubility and prevents the dehydratation as well as ring closure side reactions during the synthesis. Nterminal Gln or AsnGly (Arg, Ser, Ala, Asn) sequence may cause problems after the cleavage of the protecting group. N N H (His) p t imidazol group tertbutyloxymethyl (Bum) (p) C H 2 O C C H 3 C H 3 C H 3 The same problem as in case of Bom in Boc startegy. Don’t use it for the synthesis of peptides containing Cys at the Nterminal ! Side chain functional group protecting group name (abbreviation) N N H (His) p t imidazol group trityl (Trt) (t) Trt group protects the tN. However, its application prevents both epimerisaton (not in case of attachment to resins) and alkylation. NHCNH2 NH guanidino group C H 3 S O O C H 3 C H 3 C H 3 O 4methoxy2,3,6 trimethylbenzene sulfonyl (Mtr) (Arg) Mtr is too stable in TFA. Elevated temperature (30oC) and/or increased time (46 hrs) is necessary for effective cleavage. 1M TMSOBrthioanisol/TFA mixture is an alternative cleavage mixture that can remove Mtr more effectively. Side chain functional group protecting group name (abbreviation) NHCNH2 NH guanidino group (Arg) 2,2,5,7,8pentamethyl chroman5sulfonyl (Pmc) 2,2,4,6,7pentamethyl dihydrobenzofurane 6sulfonyl (Pbf) S O O C H 3 C H 3 C H 3 O C H 3 C H 3 S O O C H 3 C H 3 C H 3 O C H 3 C H 3 Pmc can be cleaved with TFA in 23 hrs, but Pbf protecting group can be removed times faster than Pmc. Pbf also gives rise to less sulfonated Trp byproduct than Pmc or Mtr. Use FmocArg(Pbf)OH for the synthesis of oligoArg as a cell perating peptide ! Side chain functional group protecting group name (abbreviation) indole N H (Trp) tertbutyloxycarbonyl (Boc) O O C C C H 3 C H 3 C H 3 The protection of indole side chain of Trp is not necessary, but the application of Boc group is remended. Under TFA cleavage the appearance of inN