MBHA preparation

Three generations of dendritic phosphines have been prepared from 3,5-diaminobenzoylglycine and 9-fluorenylmethoxycarbonyl-L-phenylalanine. The dendrimers were then attached to MBHA resin, treated with CH20 and Ph2PH, and converted to their Rh complexes. The polymer-supported complexes are excellent catalysts for the hydroformylation of alkenes, which could be recycled.283 The bidentate diphosphine A,A-bis-(P-(phosphabicyclo[3.3.1] nonan) methyl)aniline was prepared by phosphanomethylation of aniline. It forms a Rh-complex which is a highly regioselective catalyst in the hydroformylation of citronellene.284... 

Boc-Cys-Tyr[Z(Br)]-Ile-Gln-Asn-Cys-Pro-Leu-Gly-MBHA-resin [prepared from the corresponding S-Fm-protected resin-linked peptide (50-60mg, 0.35mmol/g, 19 nmol) by treatment with piperidine/ DMF/[5-ME (10 10 0.7) at 25 °C for 3 h] was suspended in pH 8 buffered DMF (3 mL) in an open vessel at 25 °C for 1 h, washed, deblocked with TFA/CH2C12, and cleaved with HF/anisole (9 1) at 0 °C for 1 h to provide the crude peptide yield 16 xmol (88%). This material was purified by MPLC on a Lobar RP-8 column yield 8.5 xmol (53%) the product was characterized by amino acid analysis and HPLC. 

Scheme 46 Cleavage of Peptides Containing Nucleo Alanines Prepared on MBHA Resin 83 ...

Scheme 13 Solid-Phase Preparation of Boc-Glyi >[C(—0)-S]CH2CH2C0-MBHA-Resin1671...

After preparation of the desired resin-bound peptide via SPPS, the thioester-modified product was cleaved by HF[781 from the MBHA resin179 as the amide. 

Peptide Ac-AKEAAHAEAAEAA-NH2 was synthesized using Boc chemistry on MBHA resin (100-200 mesh, 1% DVB, substitution level 0.53 mmol-g 1). Purification was carried out by HPLC on a 2.2-cm Vydac C18 column using a gradient of MeCN/H,0 in 0.1% TFA (5 to 40% over 40 min) at a flow rate of SmL-min Mesoporphyrin IX was converted into the iron(III) complex by refluxing with excess Fe(OAc)2 in AcOH.11"1 The bis(4-nitrophenyl) ester of iron(III) mesoporphyrin IX was subsequently prepared using the method of Collman et al.12001... 

Benzhydrylamines are better suited than benzylamines as acid-labile linkers for amines. The MBHA linker ( methylbenzhydrylamine ), which is usually used to prepare peptide amides (see Section 3.3), can also be used as a linker for amines (Entry 1, Table 3.21). Hydrogen fluoride is, however, required as the cleavage reagent. Easier to cleave are alkoxy-substituted benzhydrylamines (Entries 2-5, Table 3.21), which can be prepared from the corresponding benzhydryl chlorides [263] or by reductive alkylation [410] or solvolysis [411] of the Rink amide linker. In the case of benzhydrylamines linked to polystyrene as benzyl ethers, treatment with TFA can lead to the release of the linker into solution (acidolysis of the benzylic C-O bond, see Figure 3.18). 

Support-bound 1,2-diamines can be readily converted into imidazolidinones by treatment with carbonyl diimidazole [128,129]. The required diamines have been prepared on cross-linked polystyrene by reduction of peptides bound to MBHA resin with borane. Similarly, bicyclic imidazolines have been prepared from triamines and thiocarbonyl diimidazole (Entry 10, Table 14.3). Dehydration of polystyrene-bound monoacyl ethylene-1,2-diamines yields 4,5-dihydroimidazoles (cyclic amidines, Entry 5, Table 13.18). Several groups have reported the synthesis of 2-aminoimidazol-4-ones from resin-bound amino acid derivatives (e.g., Entry 6, Table 15.11). Most of these compounds are, however, unstable, and slowly decompose if dissolved in DMSO (Jesper Lau, private communication). 

Amide derivatives of benzothiazepinone 108 were prepared by solid-phase synthesis. Cleavage of 108 from the A-methylbenzhydryl (MBHA) resin was done with HF/anisole (Figure 13) <1999TL4939>. 

Other peptides in the Fcycto-MRF-NH2 series have been prepared using a more acid stable resin (MBHA, methoxybenzhydry-lamine) and Boc (t-butoxycarbonyl) protecting groups, but the Fmoc approach above gives superior yields. ... 

Preparation of sulphonyl chlorides on resin is described for MBHA, MeO-PEG and Merrifield resin... 

Protocol 1. Downloading of MBHA Resin for PNA Preparation via t-Boc/Z Chemistry. The following procedure is for loading 3 g of MBHA resin with a PNA monomer to a final range of 0.10-0.15 mmol/g and may be scaled appropriately. 

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