Glycolic acid solid support

Scheme 10.1 Glycopeptide synthesis and a-chymotrypsin catalyzed release from the solid support, a) 25% TFA (CH2CI2) b) 0-(N-Boc-Phe)glycolic acid (7 eq), BOP, HOBt, DIEA b) 25% TFA (CH2CI2) c) Boc-Gly-OH (7 eq), BOP, HOBt, DIEA c) 25% TFA (CH2CI2) d) Boc-Asn(GlcNAcb)-OH (3 eq), BOP, DIEA e) galactosyl transferase, sialyl transferase f) CT, H2O, pH 7.0 g) ultrafiltration h) a-l,3-fuco-syltransferase, GDP-Fuc (2.5 eq), 0.1 M HEPES (pH 7.0), 95%.

The Sharpless asymmetric dehydroxylation of resin-bound olefins was monitored using 3H, 13C and HMQC HRMAS NMR.63 The authors found 13C HRMAS NMR to be particularly suited to evaluating the progress of this reaction and permitted the enantiomeric excesses of the products to be determined before they were cleaved from the support. Most importantly, they were able to evaluate the types of substrates amenable to this reaction on solid supports, showing the ability of HRMAS NMR to contribute to synthetic questions. Transformation of the unnatural amino acid Lys(NH2) on a poly (ethylene glycol)-dimethylacrylamide (PEGA) resin to 6-hydroxynorleucine was confirmed by application of TOCSY HRMAS experiments.64... 

All peptide-catalyzed enone epoxidations described so far were performed using insoluble, statistically polymerized materials (neat or on solid supports). One can, on the other hand, envisage (i) generation of solubilized poly-amino acids by attachment to polyethylene glycols (PEG) and (ii) selective construction of amino acid oligomers by standard peptide synthesis-linked to a solid support, to a soluble PEG, or neat as a well-defined oligopeptide. Both approaches have been used. The former affords synthetically useful and soluble catalysts with the interesting feature that the materials can be kept in membrane reactors for continuously oper-... 

Bromo-l-ethoxyethan-l-oxy)-linked TmtaGd resin (83) To remove residual poly (ethylene glycol) from the commercially available TentaGel HL-OH resin (130 pm, 0.41 mmol OH g ), a suspension of the resin (100 g, 41 mmol) in formic acid (500 mL, 13.3 mol) was stirred at 60 °C for 14 h. The mixture was then filtered, and the resin was thoroughly washed with dioxane (1.5 L) and then treated with 1 m NaOH (300 mL, 300 mmol). After 4 h, the resin was washed with water (1 L), MeOH (1.5 L), and dioxane (1.5 L) to give the PEG-free solid support. 

The oxidation-reduction method, developed initially by Mukaiyama et al. [133] and related to the previously described organophosphorus methods, has permitted a variety of important solid-phase applications. The mechanism of the activation is complex and involves the oxidation of the triaryl/ alkyl-phosphine to the oxide as well as reduction of the disulfide to the mercapto derivative. However, different active species, such as 81 (Fig. 11), the 2-pyridyl thioester, or even the symmetrical anhydride, have been postulated to form. For the intermediate 81, the peptide bond formation may proceed through a (cyclic transition state. The method has been used for conventional stepwise synthesis [134], acylation of the first protected amino acid to a hydroxymethyl resin, and to achieve segment condensation on a solid support in the opposite direction (N C) [135,136]. Lastly, it has been used for efficient grafting of a polyethylene glycol (molecular weight 2000) derivative to an aminomethyl resin to prepare PEG-PS resins [137]. 

Invariably, dual packed columns have been employed, and one of the earliest articles devoted to the identification of petroleum products is that of Lively [4], who used dual 1.2m x 6mm columns packed with 20% SE-30 as the liquid phase and a Chromosorb solid support. Most subsequent workers in this field have employed the same or a similar liquid phase, usually at a lower loading of 4-5% and somewhat different column dimensions 1.2-3.6m x 3-6mm [5-9]. Chromosorb, or occasionally a similar solid support [7] was usually the solid support utilised after first being acid washed and treated with hexamethyl disilazine (HMDS) or dimethyl dichlorosilane (DMCS). Liquid phases of similar properties that have been employed are 5% and 10% OV-1, 20% SE-52,5% E301 [6], and 2.2% [10], 10% [13] and 20% [8] Apiezon L. These liquid phases are essentially non polar substances, but more polar phases, 5% and 10% polyethylene glycol 1500, have been used for investigations of the water-soluble components in diesel and gas oil and in petrol. 

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