Phenolic functional moieties

A second strategy is to attach a linker (also referred to as a handle or anchor) to the resin followed by assembly of the molecule. A linker is bifunctional spacer that serves to link the initial synthetic unit to the support in two discrete steps (Fig. 3). To attach a linker to a chloromethyl-PS resin, a phenol functionality such as handle 4 is used to form an ether bond (Fig. 4). To attach the same handle to an amino-functionalized support, acetoxy function 5 or a longer methylene spacer of the corresponding phenol is applied to form an amide bond. Both of these resins perform similarly and only differ in their initial starting resin [4], An alternative approach is to prepare a preformed handle in which the first building block is prederivatized to the linker and this moiety is attached to the resin. For peptide synthesis, this practice is common for the preparation of C-terminal peptide acids in order to reduce the amount of racemization of the a-carbon at the anchoring position [5],... 

In the synthesis of concave 1,10-phenanthroline cyclophanes 21 (Scheme 4), the aryl bridgeheads could be easily introduced by the addition of two aryl lithium moieties 16 to 1,10-phenanthroline (15). Although aryl lithium compounds may also be added to pyridine [23], this approach could not be realized for the construction of concave pyridine cyclophanes 29 yet [24]. Therefore another route for the synthesis of the concave pyridines 29 was used (Scheme 5) the cyclization of 1,5-diaryl substituted Cj-units 23 or 27 with ammonia. The resulting 2,6-bis(2,6-dimethoxyphenyl)pyridine 24 [25], the pyridine analogue to the tetramethoxy-1,10-phenanthroline derivative 17, was then treated in the same way. After liberation of the phenol functions, the four OH groups of 28 were reacted with two equivalents of diiodides 19 [25]. As in the synthesis of the concave 1,10-phenanthroline cyclophanes 21, two macrocycles were formed in one reaction step. 

Thiophene-1 -Carboxaldehydes Wyeth explored a set of thiophenes as new ligands for the ERs and it turned out that all compounds displayed preference for ERp [53]. Both phenolic functions were required for ER affinity and it was established that the 1-carboxaldehyde moiety significantly contributed to ERp selectivity. While replacement of the aldehyde functionality by a nitrile was well tolerated, conversion into an... 

This last compound was selectively oxidised at the vicinal diol function with sodium periodate and successively with Jones s reagent, affording the desired acid 8. Direct esterification of compound 8 with dioxy-phenyl-ethanol 14, having phenolic functions protected with benzyl moieties, gave the key intermediate secoiridoid 9. The last step of the synthesis is the stereoselective reduction of 9 that afforded the alcohol 10... 

Furthermore, it can be expatiated by considering the fact that because the proton-donating form of the functional moiety (i.e., sulphonamide) bears absolutely no charge, one may even characterize the same as an HA acid, just in the same vein as phenols, thiols and carboxyl groups. 

Cobaltocenium moieties have been attached to the calixarene skeleton by functionalizing the upper rim (opposite to phenolic functions) and such a receptor 92 can recognize dicarboxylate anions such as adipate [183, 184]. Functionalization of the upper rim and insertion of organopalladium building sites has also been reported [184a]. 

Potassium permanganate in acetone oxidation of a bisbenzylisoquinoline results in selective cleavage at the C-1 to C-a benzylic bond of the isoquinoline moiety which is unsubstituted at C-8. Relative stereochemistry does not affect the site of the oxidation. The product is an aldehydo lactam showing 1640-1645 cm" and 1690-1720 cm (5.82-5.92 and 6.08-6.17/a) which can be used for characterization purposes. The C-8 hydrogen peri to the new lactam carbonyl appears in the NMR spectrum as a singlet between 87.20 and 7.42. To exemplify, in the case of the oxidation of (H-)-hernandezine, the C-8 peri proton singlet is found at 87.23. The yields range from 5 to 35% and it is preferable to protect phenolic functions by acetylation prior to oxidation. ... 

Redox-neutral ortho-C-H alkylations of phenols can be achieved with simple alcohols in the presence of a Ru catalyst (Scheme 23.20) [83]. Using this method, several complex molecules (e.g., 16, 17, and 18) have been synthesized. Mechanistic experiments show the loss of deuterium labeling in a-position to the phenol functionality and no primary kinetic isotope effect (l jj/l p=l.l 0.1). Both findings are consistent with rapid and reversible C-H bond activation before C-C bond formation. However, the mechanism of the reaction has not been studied in detail, and the source of the unusual directing group effect of the phenol moiety is unclear. 

In recent time the number of water-soluble cryptophanes reported in the literature has increased substantially. The main reason for this arises from the rapid development of the xenon-cryptophane complexes aimed at designing biosensors for MRI applications. Nevertheless, it seems important to distinguish between two types of water-soluble cryptophanes. The first series of water-soluble cryptophanes are made from a cryptophane skeleton, which has been properly modified in order to significantly enhance its solubility in water. For instance, the hexa-carboxylate cryptophane 1 (Fig. 21.2), whose synthesis is reported below (Scheme 21.1), is sparingly soluble in neutral water and very soluble in basic solution (Na0H/H20). The second class of water-soluble cryptophanes is made of lipophilic cryptophane cores, which have been adequately functionalized in order to make the whole molecule soluble in water. For example, cryptophanol-A 2, when suitably substituted by hydrosoluble moiety at the phenol function, belongs to this second class of molecule (Fig. 21.2). Original cryptophane biosensors have been prepared by this way and will be described in more detail below. 

Anderson reported the synthesis of electron-poor PCP pincer phosphine-phosphinite 156 and performed coordination studies with platinum and palladium. The unsymmetrical pincer ligand 156 was prepared, with the P Bu2 moiety being first installed by nucleophilic attack of di-tert-butylphosphine at the benzylic carbon of 3-hydro g benzyl bromide, followed by formation of the phosphinite P-O linkage by treatment of the phenol functionality with (C6Fs)2PBr (Scheme 36). These ligands represent the first example, to date, on the incorporation of the bis(pentafluorophenyl)phosphinite moiety into a pincer ligand framework. 

Monoterpenes (Cio) are the simplest members of the terpene series. They result from the condensation of two isoprene units and may be acyclic, monocyclic, bicyclic or tricyclic. The monoterpenes can have another functional moiety like alcohol (geraniol, linalool, menthol, bomeol), aldehyde (geranial, cihonellal), ketone (menthone, carvone, thujone), ester (bomyl acetate, linalyl acetate), ether (1,8-cineol) and phenol (thymol, carvacol). In the case of optically active molecules, the proportions of the enantiomers vary largely from one species to another. 

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