Templates guanidinium

Cram reported in 1977 the use of guanidinium (a hydrogen bond-donor template) for the formation ofbenzo-27-crown-9 (1 in Scheme 1) [21,22]. Although guanidinium was not as good a template as the K+ cation, it increased the yield of macrocylisation by tenfold in comparison to the yield obtained when the... 

Related to guanidinium sulfonates are analogous cation phosphonate structures which can adopt either pillared or zeotype structures. Recently novel tubular morphologies have also been discovered for both classes of compound which may have promise for improving porosity in these types of material. At present, like the guanidinium sulfonates, few phosphonates, are really porous and removal of the guest template generally leads to the collapse of the structures.15... 

Reinhoudt and co-workers (101-105) have reported a series of Schiff base macrocyclic polyether ligand complexes prepared via barium cation-templated Schiff base condensation of the appropriate polyether dialdehyde with a diamine, in the presence of a transition metal or uranyl acetate, followed by removal of the Ba2+ template cation on subsequent addition of guanidinium sulfate (Scheme 19). The copperdl) and nickeldl) complexes (62) and (63) exhibit reversible redox couples... 

To extract DNA and RNA from serum samples or from culture supernatant fractions which contain a low level of proviral DNA, the IsoQuick extraction kit (a modified guanidinium salt-organic solvent extraction method) by MicroProbe Corporation (Bothell, WA) has been used successfully by our group. Following the manufacturer s recommended procedures for total nucleic acid extraction, the final DNA-RNA suspension can be amplified directly to detect proviral DNA. Using cDNA templates synthesized from total nucleic acids with random hexamer priming generally increases the PCR product yield. 

Y. Oishi, T. Kato, M. Kuramori, K. Suehiro, K. Ariga, A. Kamino, H. Koyano, T. Kunitake, Control of Molecular Ordering in Guanidinium-Eunctionalized Monolayer by Carboxylate Template Molecules , Chem. Commun., 1357 (1997)... 

Nonetheless, much excellent use has been made of this system. Receptor 5, for example, extracts p-nitrobenzoate quantitatively from water into chloroform (43), and the chirality of the receptor allows the possibility of chiral anion recognition (44). Guanidinium has also been incorporated into devices, such as a hydrogen sulfite selective electrode (45). Recently, Mendoza and co-workers (46) reported a chiral double helical array of polyguanidinium strands assembled around sulfate templating anions, the first anion centered helical structure. 

Sanchez-Quesada, J. Seel, C. Prados, P. de Mendoza, J. Anion helicates Double strand helical self-assembly of chiral bicyclic guanidinium dimers and tetramers around sulfate templates. J. Am. Chem. Soc. 1996, 118 (1), 277-278. 

Guanidinium ion acts as a guest in the ethereal cavity during cyclization of compound 3. A template effect is achieved through specific hard-hard hydrogen bondings (5). 

The use of the guanidinium ion [C(NH2)3] (HGu+) as a template in the synthesis of benzo-27-crown-9 was mentioned in Chapter 1 [65]. In this case the topological functions of the template centre arise from an appropriate geometry, namely an open-chain precursor of the crown ether product being accommodated around the matrix in a position suitable for ring closure by hydrogen-bond formation (Eq. 6-21). 

El Hankari, S. and Hesemann, P. (2012) Guanidinium vs. ammonium surfactants in soft-templating approaches nanostructured silica and zwitterionic /-silica from complementary precursor-surfectant ion pairs. Eur. J. Inorg. Chem., 2012, 5288-5298. 

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