Porphyrins glycosylated

Epoxidation. With Mn-salen as a catalyst, enol derivatives give 2-hydroxy acetals. Unsaturated acids form lactones during oxidation in the presence of an iron porphyrin. Glycosylation. The action of a PhlO-MejSiOTf combination on thioglycosides consists of oxidation and Lewis acid catalysis, thus allowing the synthesis of disaccharides. 

The biological significance of glycoporphyrins, their limited natural occurrence, and their widespread applications have made the availability of such compounds a scientific challenge for several research groups. Synthetic approaches have consisted in the direct glycosylation of prefunctionalized porphyrins or chemical synthesis from suitable glycoconjugates precursors. 

The second methodology involves direct introduction of glycosylated moieties onto a suitably functionalized meso-arylporphyrin scaffold, accessible from a natural source (protoporphyrin-IX) or by total synthesis. Several O-,133,145,146 S-,147 and N-glycoporphyrins148 (125-129) have thus been prepared (Fig. 12). Moreover, in order to explore the influence of the clustered peripheral saccharides around the porphyrin scaffolds, and to evaluate their photophysical properties, the synthesis of dodecavalent porphyrins bearing four trivalent glycodendrons via amide ligation (129) has been achieved.149... 

A second example has been addressed in which the synthesis and potential application of a series of neutral O-glycosylated porphyrin dimers and two original O-glycosyl cationic dimers were examined in PDT. In order to understand the influence of the number of glycosyl moieties, the spatial geometry and the ionic character on their photodynamic activity was evaluated.144 The in vitro results... 

An elegant synthesis of a monomeric porphyrin intermediate bearing one pyridyl and three glycosyl units, precursor of cationic dimers, has also been described (Scheme 18).153 Thus pyrrole, p-formylphenyl 2,3,4,6-tetra-<9-acetyl-/i-D-... 

Glycosylated porphyrins and miscellaneous products. A few other examples of functional glyco-compounds were prepared, persuing the idea that attaching a carbohydrate moiety can provide increased polarity and water solubility to another molecular construct. Many types of compounds have been prepared in this regard (Fig. 7). For example, polymerisable... 

In order to prepare asymmetric meso-porphyrinylsugar derivatives (mono-, di- and tri-glycosylarylporphyrins), pyrrole was condensed with a mixture of glycosylated and nonglycosylated aldehydes.17,21,24,44 46 Several porphyrinylsugar derivatives were prepared by this synthetic methodology. The saccharide unit can be directly linked to the porphyrin macrocycle 35-50 or separated from the phenyl group by a spacer, such as in the case of derivative 51-53 shown below (Fig. 4). 

Cationic glycosyl-bisporphyrins 66 and 6757 and a neutral porphyrin dimer 68 containing a pentapeptide moiety with RGD sequence as a spacer have also been prepared (Fig. 7).58... 

Two series of -glycosylated porphyrins have also been designed the derivatives from protoporphyrin-IX derivatization and the meso-aiy substituted porphyrins.81 83 The most comum S -glycosidic moieties on these glycoporphyrins are derived from thioglucose, thiomannose and thiogalactose. 

Since glycosylated derivatives of this porphyrin core have been shown to be effective photosensitisers, inducing necrosis and/or apoptosis in several cancer cell lines, Drain s group used TPPF20 as a core platform to efficiently generate a variety of solution-phase combinatorial libraries.83 This... 

P. Maillard, C. Huel, and M. Momenteau, Synthesis of new meso-tetrakis (glycosylated) porphyrins, Tetrahedron Lett. 33 8081 (1992). 

As mentioned before, the chemical modification of peroxidases is based on the reactivity of their exposed amino acids, besides their prosthetic group, ferroproto-porphyrin IX. As peroxidases are glycosylated enzymes, the hydroxyl groups of the carbohydrates can be modified as well (Fig. 9.1). 

Momenteau and coworkers [237] developed a series of glycosylated porphyrins where four protected sugar substituents are directly attached to the meso positions. Contrary to the observations mentioned above, the manganese complex of the xylofuranosylporphyrin (69) catalyzes the epoxidation of p-chlorostyrene to the (S)-epoxide in 20% ee [238]. Further investigations are being carried out to try to explain that result. 

Inversion of configuration (cf Epimerization) of alcohols (Mitsunobu reaction), 160-161, 286 of ally lie acetates with Pd, 27, 164 of allylpalladium with d-synthons, 27, 264 of alkyl halides or sulfonates by 1,3-dithiane anions, 22 by organylcuprates, 36 by tetracarbonylferrate<2 -X 46-47 in triorganylborane rearr., 37-38 of glycosides with free 2-OH by DAST, 272 of glycosyl halides, 271 of oxiranes by 1-alkync anions, 64, 204 by enolate type anions, 63-64 by internal alcoholate addition, 265 Inversion-esterification of alcohols, 160-161, 286 Inverted DNA , 345-346 Iodide, hydrogen porphyrin synthesis with, 255 Iodine = diiodine (Ij) ... 

Glycosylated porphyrins have also been tested as drug sensors. As examples, porphyrins lb (o) and 8b (Fig. 3) have been used for the amperometric responses to metronidazole (MTZ) and dimetridazole (DNZ), two clinically useful drugs with selective toxicity to anaerobic bacteria and protozoar-ium [77,78]. 

Fig. 3 Glycosylated porphyrins tested as drug sensors and the structures of metronidazole (MTZ) and dimetridazole (DNZ)...

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