PPY analogs

Fu and co-workers have detailed the use of planar chiral DMAP and PPY analogs as catalysts for the resolution of secondary unsaturated alcohols (Fig. 1) [15]. Both ferrocene and ruthenocene-based catalysts have been examined, with the iron-based catalysts generally proving less reactive but more selective [16]. Catalysts are prepared in racemic form and are subsequently resolved by preparative chiral HPLC. 

Scheme 15. Planar chiral PPY analog 11 as a catalyst for kinetic resolution of primary amines...

Vrang, L. and Oberg, B. (1986) PPi analogs as inhibitors of human T-lymphotropic virus type III reverse transcriptase. Antimicrob. Agents Chemother. 29, 867-872. 

In 1968 DairOlio et al. published the first report of analogous electrosyntheses in other systems. They had observed the formation of brittle, filmlike pyrrole black on a Pt-electrode during the anodic oxidation of pyrrole in dilute sulphuric acid. Conductivity measurements carried out on the isolated solid state materials gave a value of 8 Scm . In addition, a strong ESR signal was evidence of a high number of unpaired spins. Earlier, in 1961, H. Lund had reported — in a virtually unobtainable publication — that PPy can be produced by electrochemical polymerization. 

Dimethylamino)pyridine (1, DMAP) and its analogs, particularly 4-(pyrrolidino)pyridine (2, PPY) have acquired enormous importance and utility as supemucleophilic catalysts in synthetic organic and polymer chemistry (1, 2). 

The tremendous scope of utilization of DMAP and PPY as catalysts has led to an active interest in the development of their polymeric analogs. The pioneering work was carried out by Hierl et al (8) and Delaney et al. (9). They attached 4-dialkyl-aminopyridine derivatives to poly(ethyleneimine) and found the modified polymers to be highly active catalysts for hydrolysis of p-nitrophenylcarboxylates. Since then, many research groups have reported the synthesis of polymers functionalized with 4-dialkyl-aminopyridine (10-18). 

Kinetic Studies. The pioneering work of Hierl et al. (8) and Delaney et al. (9) had established that hydrolysis of jr-nitro-phenylcarboxylates was an excellent means of observing the nucleophilic catalysis by 4-(dialkylamino) pyridine functionalized polymers. Hydrolysis of p-nitrophenylacetate in a buffer at pH 8.5 showed that the polymer was a slightly better catalyst than the monomeric analog PPY (Table II). However, preliminary results indicate that the polymer bound 4-(dialkylamino) pyridine is more effective as a catalyst than the monomeric analog in the hydrolysis of longer carbon chain p-nitrophenylcarboxylates, such as p-nitrophenylcaproate. 

Our group described a simple access to well-defined hyperbranched polyamines from hyperbranched PEI with different molecular weights, narrow molecular weight distributions, and an adjustable degree of branching [91]. According to this protocol fully branched analogs of polypropyleneimine (PPI) and polyamidoa-mine (PAMAM) dendrimers can be derived from hyperbranched PEI (Mw = 5,000, and 25,000 g mol-1) in a two-step synthetic process (Scheme 2). 

In case of equilibrium, addition of labeled PPi yields labeled ATP and this product can be employed to detect NRPS or related enzymes. The respective reaction rates provide information on adenylate formation/pyrophosphoiylysis, apparent Km of substrates and substrate analogs, and with some enzyme kinetic efforts, substrate affinities and the patterns of substrate binding may be deduced. The ease and the sensitivity of the procedure makes it the primary method of investigation of NRPS substrate specificity. 

Neutral Ir complexes were obtained by an orthometalation reaction with ligands that contain a benzene ring attached to a functional group containing a donor atom such as 2-phenylpyridine (ppy) and benzo[h]-quinoline (bzq) [93]. The coordination of ppy and bzq ligands to metal is analogous to... 

Because of its analogy to PPi and an ability to chelate metals, the BP structure has served as a pharmacophore for drug design in various areas. In addition, as detailed in Chapter I—1, "...in some cases a new clinical activity observed for an old drug is sufficiently potent and interesting to justify the immediate use of the drug in the new indication... . Some of the cases that follow fall into this class, and include especially antiparasitic, anti-arthritic, and antirestenosis applications. 

The next group of materials comprises conducting polymers (ICP). Systems with identical polymers have often been reported for polyacetylene. It is known that this ICP forms insertion compounds of the A and D types (see Section 6.4, and No. 5 in Table 12). Cells of this Idnd were successfully cycled [277, 281-283]. However, the current efficiency was only 35% heavy losses were observed due to an overoxidation of the PA [284]. In other cases as for polypyrrole (PPy), the formation of D-PPy was anticipated but did not occur [557, 558]. Entry (6) in Table 12 represents some kind of ideal model. A PPy/PPy cell with alkyl or aryl sulfates or sulfonates rather than perchlorates is claimed in [559]. Similar results were obtained with symmetric polyaniline (PANI) cells [560, 561]. Symmetric PPy and RANI cells yield about 60% current efficiency, much more than with PA. An undoped PPy/A-doped PPy combination yields an anion-concentration cell [562, 563], in analogy to graphite [47], (cf. No. 7). The same principle can be applied with the PPy/PT combination [562, 563] (cf. No. 8). Kaneto et al. [564] have reported in an early paper the combination of two pol54hiophene (PT) thin layers (< 1 pm), but the chargeability was relatively poor (Fig. 40, and No. 9 in Table 12). A pronounced improvement was due to Gottesfeld et al. [342, 343, 562, 563], who employed poly[3-(4-fluoro-phenyl)thiophene], P-3-FPT, in combination with a stable salt electrolyte (but in acetonitrile cf. Fig. 40 and No. 10 in Table 12). In all practical cases, however, Es.th was below 100 Wh/kg. 

Reetz et al.59 have introduced polypropylenimine (PPI) dendrimers as the core for building phosphine-coated constructs that can complex with Rh(COD) BF4, where COD = 1,5-cyclooctadiene, to instill the desired catalytic character. Hydroformylation of 1-octene with these metallodendrimers was shown to have turnover numbers that were comparable to those of monomeric analogs. It was pointed out that these catalysts could be easily recovered by means of membrane separation technology.60 Gong et al. have used water-soluble, phosphonated dendritic... 

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