Merrifield s resin

Difficulties due to side reactions (cyclization) and a broad molecular weight distribution accompanying the polycondensation of active esters led to the application of methods wherein the polymers are built up stepwise. In 1968, Sakakibara et al.31) introduced the solid-phase technique using Merrifield s resin. By stepwise addition of tert-pentyloxycar-bonyl tripeptides, they have synthesized (Pro-Pro-Gly)n with n = 5, 10, 15 and 20. 

The Dupont method to prepare polymer-supported bidentate phosphorus-containing ligands makes use of Merrifield s resin (Scheme 10).69... 

Starting from the corresponding hydroxymethyl-benzocrown, it has been possible to generate the immobilized system (186) by reacting the above precursor with chloromethylated polystyrene (which is available commercially as Merrifield s resin). Typically, systems of this type contain a polystyrene matrix which has been cross-linked with approximately 1-4% p-divinylbenzene. In one study involving (186), a clean resolution of the alkali metal halides was achieved by HPLC using (186) as the solid phase and methanol as eluent (Blasius etal., 1980). In other studies, the divalent alkaline earths were also separated. 

Initial solid phase synthesis25 was carried out on Merrifield s resin (1 % crosslinked chloromethylated styrene/divinylbenzene copolymer, 200-400 mesh) because of its track record in solid-phase peptide synthesis.26 Unfortunately, the Merrifield resin has limitations as a carbohydrate carrier to study interactions between the carbohydrates and relevant binding proteins. The hydrophobic nature of the resin leads to nonspecific, irreversible protein adsorption.27 Later work utilized Rapp s TentaGel, an amphiphilic, polyethylene glycol resin.28... 

Smith and Liu have successfully prepared an unsymmetrical analog of a Katsui-type salen ligand possessing a hydroxyalkyl group in the 6-position, which facilitated the formation of an ester Hnkage to a polystyrene carboxyl chloride resin (Figure 5.19) derived from Merrifield s resin (chloromethylated polystyrene,... 

Figure 5.19 Unsymmetrical Katsui-type Mn complex immobilized on Merrifield s resin [72].

Figure 4.4. Attachment of benzenediazonium salts to n-propylaminated Merrifield s resin monitored by gas chromatography. Completion of the reaction corresponds to increased concentration of triazene.

Figure 4.8. Cases 1 and 2 (Table 4.6) calculated yields for n-propylamination of Merrifield s resin versus chronological reaction attempt.

Smith and Liu <02CC886> have immobilized a Katsuki-type salen ligand by an ester linkage to Merrifield s resin to produce catalyst 7. In a test epoxidation of 1,2-dihydronaphthalene (8)... 

A frequently investigated approach is based on Merrifield s resin, which is a polystyrene polymer [6]. 

The Step 3 product (4.00 mmol) was dissolved in 100 ml of THF and then cooled to —78°C and treated with 2.7ml of n-BuLi (4.32mmol 1.6M in hexane). It was stirred for 30 minutes, followed by 4 additional hours of stirring at ambient temperature, and then concentrated. The residue was washed twice with 15 ml of n-hexane, dissolved in 150 ml of THF containing 1% Merrifield s resin (2.0 g 3.94 mmol Cl), and stirred at ambient temperature for two days. The mixture was refluxed for 4 hours and then quenched with 3.0 ml of methanol and re-concentrated. The residue was washed twice with 10 ml of deionized water and twice with 20 ml of n-hexane. The solid was dried, and 2.40 g polystyrene-supported ortho-carborane were isolated as a pale yellow solid. 

Most oligosaccharide syntheses have relied on Merrifield s resin [polystyrene (PS), cross-linked with 1% divinylbenzene], which was originally a nitrated chloro-... 

Schmidt et al. [62] have described the synthesis of oligomannosides using an alkyl thiol containing linker connected to Merrifield s resin. Mannosyl trichloroacetimi-date was activated with TMSOTf. The fully protected oligomannoside was released from the solid support by oxidation (NBS/DTBP) (Scheme 20.19). 

PEG (average MW 5000) was selected as soluble support, whereas for solid phase synthesis Merrifield s resin and an additional spacer was employed to reduce steric hinderance imposed by the solid phase. 

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