Carbonate ester templates

Figure 11 Structures of the intravenous anesthetic propofol 13 and the carbonate ester template of propofol 14 (Ref. 17).

Figure 12 Carbonate ester templates (a) based on 2-hydroxyethyl methacrylate 15 (adapted from Ref. 5) (b) based on allyl alcohol 16 (adapted from Ref. 18).

Whitcombe et al. observed a strong decrease of the cholesterol concentration, and hence excellent binding for cholesterol with p(EGDMA-co-CVPC) shell/ pMMA core particles in isohexane. When the carbonate ester was not hydrolyzed and hence no imprinted sites existed in the shell, only 2.7 pmol cholesterol per g particles were bound corresponding to the non-specifically adsorbed templates. Slightly less cholesterol was adsorbed to particles prepared without CVPC at all thus formed with a pure pEGDMA shell (<2 pmol g-1). 

In an earlier investigation by the author [ 1 ] 1 -benzotriazolyl carbonate esters of poly(ethylene glycol), (I), were prepared and used as drug delivery templates for lysine and lysozyme. 

Figure 7 Sacrificial spacer method, as exemplified by the imprinting of cholesterol (a) cholesteryl (4-vinyl)phenyl carbonate 8 is used as the template monomer to form a covalently imprinted polymer (b) in the polymerization step, the carbonyl group of the carbonate ester holds the functional monomer and template oxygen atoms apart by two bond distances (c) hydrolysis results in loss of the template and loss of the spacer as CO2 (d) rebinding can now occur with the cholesterol ligand occupying essentially the same space as the template cholesteryl group (adapted from Ref. 10).

Highly selective MIP-coated quartz crystal microbalance (QCM) sensors have been prepared for nandrolone [16], a performance-enhancing substance that has been banned in international sports. The authors hope to address the need for a sensor to rapidly detect this substance of abuse. MIP was prepared with a 4-vinylphenol carbonate ester of the template, but also in the presence of methacrylic acid to target the ketone functionality. The sensor was able to detect nandrolone down to 0.2 ppm and was highly selective over closely related structures such as testosterone and epitestosterone. 

Chiral diester diamide macrocycles such as ll-180 have been synthesized (181) from esters of L-valine by, first of all, forming acyclic bisamides and then hydrolyzing the ester functions prior to template-promoted cyclization with cesium carbonate (182) and the appropriate dibromide. L-Tartaric acid has also been incorporated into a macrocycle, i.e., lll-181, of this type. 

Template reactions between malonaldehydes and diamines in the presence of copper(II), nickel(II) or cobalt(II) salts yield neutral macrocyclic complexes (equation 15).99-102 Both aliphatic102 and aromatic101 diamines can be used. In certain cases, non-macrocyclic intermediates can be isolated and subsequently converted into unsymmetrical macrocyclic complexes by reaction with a different diamine (Scheme ll).101 These methods are more versatile and more convenient than an earlier template reaction in which propynal replaces the malonaldehyde (equation 16).103 This latter method can also be used for the non-template synthesis of the macrocyclic ligand in relatively poor yield. A further variation on this reaction type allows the use of an enol ether (vinylogous ester), which provides more flexibility with respect to substituents (equation 17).104 The approach illustrated in equation (15), and Scheme 11 can be extended to include reactions of (3-diketones. The benzodiazepines, which result from reaction between 1,2-diaminobenzenes and (3-diketones, can also serve as precursors in the metal template reaction (Scheme 12).101 105 106 The macrocyclic complex product (46) in this sequence, being unsubstituted on the meso carbon atom, has been shown to undergo an electrochemical oxidative dimerization (equation 18).107... 

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