Pyran polymer

Many other polymers have been tested as backbonesfor prodrugs. As examples, one may list poly-L-(glutamic acid) for clonidine controlled release (52), hyaluronic acid for hydrocortisone and derivatives (53-55), or the synthetic polyanionic polymer pyran for the antitumor, antibacterial, and antiviral agent muramyl dipeptide (56). Hyaluronic acid and pyran are interesting in the sense that they add a new dimension to the macromolecular prodrug approach. Hyaluronic acid is believed to be potentially useful for the control of infec-... 

Among all the polyanionic polymers, pyran copolymer [6] and carbetimer [7] have been extensively studied, both in the laboratory and in preclinical and clinical trials. The results are interesting and could be helpful for the elucidation of various biological mechanisms, even though the activities are not high enough for either of these polyanions to be considered for a phase III trial at this time [5]. 

Furfural — see Furan-2-oarbaldehyde, 532 Furfuryl acetate, o -(butoxycarbonyl)-anodic oxidation, 1, 424 Furfuryi acrylate polymerization, 1, 279 Furfuryl alcohol configuration, 4, 544 2-Furfuryl alcohol polyoondensation, 1, 278 reactions, 4, 70-71 Furfuryl alcohol, dihydro-pyran-4-one synthesis from, 3, 815 Furfuryl alcohol, tetrahydro-polymers, 1, 276 rearrangement, 3, 773 Furfuryl chloride reactions... 

Pyran-2,6-dicarboxylic acid, 4-oxo-, 3, 692, 703, 710 diethyl ester polymers, 1, 288 synthesis, 3, 811... 

H-Pyran-2,4-dione, 3-acetyl-6-methyl-food preservative, 1, 410 Pyran-2,6-dione, tetrahydro-polymers, 1, 313 Pyrandiones synthesis, 3, 793... 

In connection with studies on the ring-opening polymerization of cyclic acetals, we have undertaken investigations on the polymerization of bicyclic acetals, bicyclic oxalactone, and bicyclic oxalactam, which yield polysaccharide analogs, macrocyclic oligoesters, and a hydrophilic polyamide, respectively, some of which can be expected to be useful as novel speciality polymers. The monomers employed in the studies were prepared via synthetic routes presented in Scheme 1, starting from 3,4-dihydro-2H-pyran-2-carbaldehyde (acrolein dimer) I. 

Asymmetric Diels-Alder reactions have also been achieved in the presence of poly(ethylene glycol)-supported chiral imidazohdin-4-one [113] and copper-loaded silica-grafted bis(oxazolines) [114]. Polymer-bound, camphor-based polysiloxane-fixed metal 1,3-diketonates (chirasil-metals) (37) have proven to catalyze the hetero Diels-Alder reaction of benzaldehyde and Danishefsky s diene. Best catalysts were obtained when oxovanadium(lV) and europium(III) where employed as coordinating metals. Despite excellent chemical yields the resulting pyran-4-ones were reported to be formed with only moderate stereoselectivity (Scheme 4.22). The polymeric catalysts are soluble in hexane and could be precipitated by addition of methanol. Interestingly, the polymeric oxovanadium(III)-catalysts invoke opposite enantioselectivities compared with their monomeric counterparts [115]. 

Ceroplastol synthesis, 1, 428 Cetyl alcohol synthesis, 1, 478 Chaetoglobasins structures, 4, 376 Chalcone, a-azido-2 -oxy-synthesis, 3, 823 Chalcone, 2-hydroxy-reduction, 3, 751 Chalcone, 2 -hydroxy-mass spectra, 3, 618 Chalcone dibromides flavone synthesis from, 3, 823 Chalcones polymers, 1, 304 Chanoclavine synthesis, 6, 423 Charge density waves in stacks of ions, 1, 351-352 Chartreusin antibiotic, 3, 677 Chelating agents as pharmaceuticals, 1, 158-159 Chelating resins for metal ions, 1, 290 vinylimidazolecarboxylic acid as, 1, 281 Chelidonic acid — see Pyran-2,6-dicarboxylic acid, 4-oxo-... 

The submitters report that /3-methylglutaraldehyde may be isolated at this point from an analogous hydrolysis. The hydrolysis is carried out with 196 g. of 3,4-dihydro-2-methoxy-4-methyl-2H-pyran in 650 ml. of water and 15 ml. of concentrated hydrochloric acid for 3 hours. After neutralization with sodium bicarbonate, the solution is saturated with sodium chloride and extracted continuously with ether for 20 hours. The ether is removed by distillation, and the product is dried thoroughly by azeotropic distillation using a benzene-hexane mixture. Distillation affords /3-methylglutaraldehyde, b.p. 85-86°/15 mm., 1.4307-1.4351. Yields up to 90% have been secured. The aldehyde polymerizes on standing but is stable as a 50% solution in water or ether. The monomer may be recovered by careful destructive distillation of the polymer. 

The copolymerisation of CO2 and l,4-bis-(Al,IV-diethylamino-ethynyl)benzene affords a quantitative yield of a poly(pyran-4-one) (Mn 10000) without the need for a catalyst. Its repeat unit has been synthesised to assist in the structure elucidation of the polymer (95CC2417). 

There are thousands of phenolic compounds in plants, divided into several classes according to their structures. The simplest structures are Cs, Q-Q ben-zenic compounds such as benzoic acids (Figure 16.1a), and C6-C3-C6 compounds composed of two benzenic rings (A and B) and a heterocyclic pyranic ring C, characteristic of flavonoids (Figure 16.1c). The more complex are in general polymers of these structures. 

Compared with 49, 2,5-dioxabicyclo[2.2.2]octan-3-one (54) prepared from sodium 3,4-dihydro-2//-pyran-2-carboxylate has a much low polymerization reactivity [54] Lewis acids such as antimony pentachloride, phosphorus pentafluoride, and boron trifluoride etherate were not effective at all to initiate the polymerization of 54. Trifluoromethanesulfonic acid induced the polymerization of 54, but the yield and molecular weight of the polymer were low. Bicyclic lactone 54 was allowed to polymerize with anionic and coordination initiators such as butyl-lithium, lithiumbenzophenone ketyl, and tetraisopropyl titanate. However, the... 

Not only PVNO [1] but also the so-called pyrane copolymer stimulated the study of the physiological properties of synthetic polymers. This cyclic copolymers [5] from divinyl ether and maleic anhydride, first time described by Regelson (38), induces the formation of interferon. 

A. Miyashita, S. Nakano, M. Hirano, and H. Nohira, Negative photochromic polymers. Synthesis and photochemical properties of poly(methyl methacrylate) having spirobenzoselenazolinobenzo-pyran side groups, Chem. Lett., 1993, 501-504. 

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