Proof-of-concept

The project started in November 1995. The first reaction involved the hydrogenation of cydohexene in SCGO2 [Eq. (1)]. The results were striking, with a quantitative conversion being observed. The reaction proceeded with a very high linear hourly 

4 Towards Biphotonic Microscopy Imaging 5.4.1 Proof of Concept 

In 2007, our group reported the hrst microscopic observation of two-photon excited Tb(III) emission, in bulk crystals of tris-dipicolinate complex or in protein crystals (e.g., HEWL, hen eggs white lysozyme [102]) doped with the same complex supress crystals [60]. In spite of the very low 2PA efficiency of this complex, the microscopy experiment was successful 

Following this initial report, several groups have used already existing complexes for multi-photon microscopy [62,88,103,104]. All these complexes, described in Fig. 5.15, are stable and soluble in aqueous media. Furthermore, they are able to stain cells and do not present significant cell toxicity. But, since they were not especially designed for two-photon application (no CT excited state is present in the sensitising chromophore), their unoptimised two-photon cross-sections are low ( 10GM). 

All those examples and some others [105] clearly illustrate the feasibility of multi-photon imaging microscopy using lanthanide complexes as probes. However, the very low nonlinear efficiency of these complexes is slightly compensated by the increase of the incident laser power intensity to obtain well resolved images, but this clearly remains an important drawback for any practical applications. 

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It should be noted that these results are only preliminary and have to be considered as a proof of concept. As is clear from eq. (2) the phase contrast can be improved drastically by improving the global resolution and sensitivity of the instrument. Currently, a high resolution desktop system is under construction [5] in which the resolution is much better than that of the instrument used in this work, and in which the phase contrast is expected to be stronger by one order of magnitude. 

Since the original proof of concept, and a later demonstration of its practical use in semiconductor manufacturing (40), appHcations and extensions of this concept have proliferated. In the following sections these systems are described in greater detail with emphasis on the resist formulation at a components level (41). 

Similar to levels planned for proof of concept (POC) tests. 

Szallasi A, Cortright DN, Blum CA et al (2007) The vanilloid receptor TRPV1 10 years from channel cloning to antagonist proof-of-concept. Nat Rev Drug Discov 6 357-372... 

As the Diels-Alder reactions of 2( lff)-pyrazinones with richly substituted acetylenes can be used to generate diversely substituted pyridines and pyridi-nones, these cyclo additions were investigated under microwave irradiation conditions on the 1,2,3-triazole decorated pyrazinone scaffold. As a proof of concept, the pyrazinones bearing a 1,4-disubstituted-1,2,3-triazole unit, linked via a C-0 bond, were reacted with the symmetrical dienophile dimethyl acetylenedicarboxylate (DMAD), in view of minimizing regioselect-ivity problems (Scheme 28). 

For the solid-phase experiments [115], the commercially available Wang and HMPB-AM resins were chosen due their stability under the applied reaction conditions and an easy cleavage with TFA/DCM mixtures. Moreover, a novel, tailor-made and readily available linker, derived from inexpensive syringaldehyde was designed and proven to be superior to both standard Wang and HMPB-AM resins. For an initial study, as a proof of concept , the Wang linker was mimicked with a 4-methoxybenzyl group at N-1 position of a pyrazinone, and the sequence was evaluated in solution (Scheme 41). 

Figure 26. Block diagram of the proof of concept 589 nm CW fiber laser system.

Consequently, S-1360, a triazole analogue of DKA, was the first integrase strand transfer inhibitor (INSTI) to enter clinical trials, but the development was stopped during phase Eli (Billich 2003). Subsequently, a novel series of potent INSTIs, which replaced the 1,3-diketo acid moiety by an isosteric 8-hydroxy-1,6-naphthyridine core, showed improved metabohc stabihty (Zhuang et al. 2003). The compound L-870,810 moved into clinical trials, where it provided proof of concept in antiretroviral therapy-experienced and antiretroviral therapy-naive... 

Gu X, Simons KJ, Simons FER Administration by sublingual tablet feasible for the first aid treatment of anaphylaxis A proof-of-concept study. Diophar Drug Dispos 2002 23 213-216. 

Proof-of-concept through new pharmaceuticals. We have generated preliminary data suggesting that one of Rumphius s purported pharmaceuticals does have the medicinal properties described. However, it has not been shown that the active compound is novel. Examining other plants identified in historic herbal texts for their purported medicinal properties may ultimately show that novel pharmaceuticals can be developed by mining historic herbal texts. 

FIGURE 5.2 Clinical outcome of patients in the double-blind, proof-of-concept trial evaluating EPO in acute stroke, (a) Barthel Index (rhEPO vs. placebo, p < 0.05). (b) Modified Rankin Scale (rhEPO vs. placebo, p < 0.07) on day 30. Dead patients received the worst possible score. Evolution of lesion size of patients in the efficacy trial of Albumin in acute stroke, ((a-1) and DWI and (a-2) FLAIR.) (Reprinted with permission from reference 50.)... 

The reported in situ NMR of combustion [2] served largely as proof of concept work. It was demonstrated that despite the presence of paramagnetic oxygen and radicals, the xenon relaxation times are sufficiently long for gas exchange studies. 

Given the relative simplicity of ligand-based methods, it is interesting to note that in only comparatively few published reports of VS successes do the authors rely primarily on ligand-based methods. Of these studies, most appear to combine an interest in a given target with an interest in providing proof-of-concept for some extension of chemoinformatic theory. 

Haringman JJ, Kraan MC, Smeets TJ, Zwinderman KH, Tak PP. Chemokine blockade and chronic inflammatory disease proof of concept in patients with rheumatoid arthritis. Ann Rheum Dis 2003 62(8) 715-721. 

Based on these results, proof of concept was established for application of this chemistry. However, there were a few issues that needed to be addressed prior to scale up, namely preparation of the chiral ligand 31 and preparation of the Mo... 

The above sequence was demonstrated on racemic onti-mercaptol alcohol 14 as well on a small amount of optically pure 14 (separated by chiral HPLC separation) and the chiral centers of 14 were completely retained, as expected (Scheme 5.6) [8]. With proof of concept for the ring formation strategy, some efforts were put into developing a chiral synthesis of 14, as shown in Scheme 5.7. 

With this encouraging result from the model system, a gram quantity of the racemic sulfoxide 40 was prepared by oxidation of benzoxathiin 16 with mCPBA and a small amount of chiral sulfoxide (A)-40 with 94% ee was isolated by subsequent chiral HPLC separation (Scheme 5.12). When chiral sulfoxide (S)-40 was treated with borane-dimethylsulfide, a clean reduction of the olefin and the sulfoxide was observed. More surprisingly, only the desired cis-diaryl dihydrobenzoxathiin 12 was observed in high yield and unchanged 94% ee. No trans-isomer or 16 was observed. With this proof of concept in hand, an efficient... 

Scheme 5.12 Sulfoxide-directed olefin reduction-proof of concept.

With proof-of-concept on the direct methylation in hand, the optimization of the methylation with respect to regioselectivity, yield and isolation conditions was initiated to eliminate the use of 1,4-dioxane and LiH (Table 6.3). Under similar reagent/base conditions (Me2S04, LiOt-Bu), better selectivity was observed in nonpolar solvents (entries 2 and 3) than in polar (entry 1) and aprotic solvents (entries 4 and 5). Mel was a better methylation reagent than dimethyl sulfate under otherwise the same reaction conditions (entries 5 and 7). 

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