Sieber-amide resin

Geert-Jan Boons et al. also synthesized peptidoglycan fragments such as the disaccharide repeating unit [51] and muramyl peptide derivatives containing Lys and DAP residues [52-55] obtained through cross olefin metathesis [56], The muramyl peptides, such as 48 prepared by solid-phase synthesis on Sieber amide resin (Scheme 14.6), were subjected to biological and structural analyses [50, 57, 58] of... 

Boons and co-workers synthesized an analog of the structure of the cross-linked peptidoglycan (17) as well as MPP (both Lys and meso-DAP type and their truncated peptide analogs, bis-, tri-, tetrapeptides) (3) using hyperacid sensitive Sieber amide resin (18) as solid-phase support. 

Carrier - Chloromethyl-Polystyrene (Sieber-Amide resin)... 

Several linkers have been developed that rely on the formation of highly stabilized aromatic carbocations. The most frequently used are the eponymous Sieber amide linker 36 [3] and Barany s 3-XAL linker 6 [4]. Both are based on a 3-methoxyxanthine scaffold, which owing to the highly stabilized nature of the xan-thenium ion can provide primary amides on treatment with 1% TFA in DCM, making them excellent tools for the synthesis of protected peptide carboxamides. The Sieber amide resin has also been used to prepare secondary amides via reductive alkylation of the amino group, acylation of the resultant amine and cleavage with dilute TFA [88]. Brill et al. [67] have effected transamination of trifluoroacety-lated Sieber amide resin in good yield. This approach offers considerable potential for the immobilization of amines on this support. 

An idenhcal approach was followed for the preparahon of combinatorial libraries from ursohc acid, betulinic add, and lupeol (Figure 11.50). In the case of betuhnic acid (105) and ursohc acid, the triterpene scaffold was immobilized onto a prederivatized amino acid on 2-chlorotrityl or Sieber amide resin, and treated with a variety of ahphahc, aromatic, and amino acids, to generate a library of C-3 and C-28 derivatives 106.In another series, C-3 oxime esters 107 were prepared from... 

Greater acid lability has been achieved using the xanthenyl derivatized resin, 9-(fluorenylmethoxycarbonylamino)xanthen-3-yloxymethyl polystyrene (Sieber amide) resin 3 (9,10), which besides being cleavable by 1% v/v TFA, holds the added advantage of readily undergoing reductive N-alkylation to afford resin-bound secondary amines for the synthesis of peptidyl iV-alkyl... 

Fmoc-amino)xanthen-3-yloxymethyl polystyrene (Sieber amide) resin... 

Pre-sweil the 9-(Fmoc-amino)xanthen-3-yioxymethyl polystyrene (Sieber amide) resin (0.05 mmol, ca. 100 mg) in DCM for 1 h in a peptide synthesizer column. 

Benzhydryl- (phenylbenzyl) and 4-methylbenzhydrylamine resins (see Section 5.18) are available for preparing primary amides, using Boc/Bzl chemistry. 4-Methylben-zhydrylamine, Rink amide, Sieber amide and dhnethoxytritylamine resins and the linkers PAL and XAL (see Section 5.20) are available for preparing primary amides, using Fmoc/tBu chemistry. Secondary amides can be synthesized by making use of AJ-alkyl-Sieber or ALalkyl-PAL linkers. 

Ruik amide resin 2 RiIrean 3 Sieber resin... 

Attachment ofS-hydroxymeihylfutfural to Sieher resin To resin-bearing succi-nylated Sieber amide (271) (100 mg, Novabiochem, 0.63 mmol g ) was added 5-hydroxyfurfural (6 equiv., 32 pL, 0.378 mmol), DIC (6 equiv. 48 pL,... 

Chloromethyl resin Wang resin 2-Chlorotrityl resin Rink amide resin Hydroxymethyl resin Sasrin resin Sieber resin Aldehyde resin PAL amide resin TentaGel S NH2... 

Hydroxyethylene resin HMPA resin Chloromethyl resin Hydroxymethyl resin Tritylchloride resin Rink amide resin Wang resin REM resin Aminomethyl resin Chloromethyl resin Wang resin Rink amide resin PAL amide resin MBHA resin Chloromethyl resin Chlorotrityl resin Wang resin PAM resin Polystyrene resin Chloromethyl resin Chlorotrityl resin Wang resin Rink amide resin Sasrin resin Polystyrene resin Chloromethyl resin Benzoic acid resin Wang resin Trityl resin 2-Chlorotrityl resin PAL resin Rink amide resin MBHA resin REM resin Hydroxymethyl resin Polystyrene Aminomethyl resin Chloromethyl resin 2-Chlorotrityl resin Hydroxyethyl resin Rink amide resin Wang resin MBHA resin Sieber resin... 

In addition to the procedures listed in Table 3.38, further reactions have been used to generate halides upon cleavage. In Section 3.5.2, iodolactonization is presented as a method for the preparation of iodomethyl lactones from resin-bound pentenoic or hexenoic acid derivatives. Closely related to the iodolactonization is the iodine-mediated formation of 2-(iodomethyl)tetrahydrofurans from resin-bound isoxazoli-dines (Entry 9, Table 3.38 for the mechanism, see Figure 15.5). Nitriles can also be prepared by cleavage and simultaneous dehydration of amides RCONH2 from the Rink or Sieber linkers with TFA anhydride (Entry 10, Table 3.38). 

Xanthenyl resin, a highly add-labUe resin suitable for SPPS of proteded peptide amide segments [P. Sieber, Tetrahedron Lett. 1987, 28, 2107]. 

---