Diastereoselective synthesis of the polyol-containing side chain of the ent-bengamides

The synthesis of the non-natural antipode of the bengamide polyol-containing side chain has been achieved utilizing a diastereoselective oxygenated-enolate aldol reaction as the key step. A substrate-controlled reduction was used to complete the stereochemical array.     

Diastereoselective protonation of dienols: a formal approach to zaragozic acid C side chain

The 2-methyl 5-phenylpropanal precursor of the side chain of zaragozic acid C has been prepared in 83% ee through the diastereoselective protonation of a photodienol generated in situ by irradiation of an α,β-unsaturated ester, bearing, as a chiral moiety, the diacetone d-glucose group.     

Syntheses of vinyl polymers containing the N-phenothiazinyl group in the side chain

Four kinds of vinyl polymers containing N-substituted phenothiazinyl groups in side chains were obtained by syntheses of the respective monomers and subsequent polymerizations. Thus, N-acrylamidomethylphenothiazine, N-(N-acrylamidomethyl)carbamoylethyl phenothiazine, β-(N-phenothiazinyl)ethyl acrylate and methacrylate, and β-(N-phenothiazinyl)ethyl vinyl ether were synthesized. It was found that all monomers except the last monomer can be polymerized with typical free-radical initiators such as α,α′-azobisisobutyronitrile to afford stable soluble polymers with electron-donating characteristics, presumably due to the absence of a hydrogen atom at the site of the nitrogen atom of the phenothiazinyl group. The last monomer was found to be susceptible to typical cationic initiators such as boron trifluoride etherate to afford a stable soluble polymer also with the electron-donating characteristic.     

Synthesis of α-tocopherol and naphthotocopherol analogs with a carboxyl group in the side chain

On the basis of ozonolysis of short-chain α-tocopherol and naphthotocopherol analogs with a terminal isopropylidene group in the side chain, a general approach to the synthesis of 6-hydroxy-2,5,7,8-tetrtamethylchroman-2-yl-and 6-hydroxy-2,5-dimethyl-3,4-dihydro-2H-naphtho[1,2-b]pyran-2-ylpropionic and-acetic acid derivatives, which are hydrophilic tocopherol analogs, was proposed. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 299—304, February, 2006.     

Diastereoselective photochromism of a bisbenzothienylethene governed by steric as well as electronic interactions

Introduction of an asymmetric center to C-2 of one of the benzothiophene rings of bisbenzothienylperfluorocyclopentene results in a highly diastereoselective photochromic system. The stereogenic center bears a hydrogen atom, a methyl group, and a methoxymethoxy group. The steric as well as the electronic repulsions gave an 87-88% diastereomer excess in various solvents at room temperature with 80-85% conversion to the colored form. The enantioselective synthesis was also carried out. Upon photoirradiation in hexane, a change in optical rotation at 820 nm, where neither the open form nor the colored form absorbs light, was observed repeatedly.     

Structure and surface properties of polyacrylates with short fluorocarbon side chain: Role of the main chain and spacer group

The degradation of poly(fluoroalkyl acrylate)s with long perfluoroalkyl groups, especially with perfluorooctyl group, leads to the release of biopersistent perfluorooctanoic acid (PFOA) or perfluorooctanesulfonic acid (PFOS). To find the environmentally friendly substitutes, a series of nonbiopersistant fluorinated polymers containing perfluorohexyl groups in the side chains have been synthesized and characterized. This study was then focused on the role played by the main chain and spacer group located in the side chain between the backbone and the fluorinated segment and, in particular, on the properties of poly[2‐[[[[2‐(perfluorohexyl)]‐sulfonyl]methyl]amino]ethyl] acrylate (PC6SA), methacrylate (PC6SMA) and poly[(perfluorohexyl)ethyl] methacrylate (PC6MA). Surface properties and bulk organization of fluorinated side chains of those polymers were investigated by contact angles, differential scanning calorimetry, optical polaring microscopy, and wide‐angle X‐ray scattering. Results were compared with those obtained with poly[(perfluorohexyl) ethyl] acrylate (PC6A). They all had very low surface free energies. Surprisingly, with the same perfluoalkyl chain, PC6SA and PC6SMA with a N‐methylsulfonamide spacer group were found to be organized in a liquid crystalline lamellar structure, whereas PC6A and PC6MA were found to be amorphous. This was mainly attributed to the steric term and polarity of N‐methylsulfonamide group that tended to facilitate the orientation of the perfluorinated segments in smectic phases. PC6SA, PC6SMA, and PC6MA had rich dynamic water repellency because of the low surface molecular mobility. This phenomenon relates to the crystallization of side chains or high glass transition temperature. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2584–2593, 2010     

Solvent effect on photochromism of a dithienylperfluorocyclopentene having diethylamino group

Some photochromic diarylethenes having polar substituents were synthesized, and their photochromic behavior was examined. They exhibited photochromism with the similar photoreactivity in a non-polar solvent. However, the photocyclization quantum yield of dithienylperfluorocyclopentene having diethylamino group was found to decrease in polar solvents. The yield in acetonitrile was estimated to be 60 times smaller than that in hexane. The yields determined in various solvents were found to be correlated with the solvent polarity parameter E_T(30). Such an effect was not observed in dithienylfluorocyclopentenes bearing methoxy or acetoxy group and in non-fluorinated dithienylcyclopentene bearing diethylamino group.     

The synthesis and characterization of organometallic copolymers with Mn-Re binuclear transition-metal group in the side chain

Novel organometallic copolymers with Mn-Re binuclear transition-metal groups in the side chain are synthesized and characterized. The structure and properties of the copolymers are characterized by GPC, DSC, TG, NMR, FT-IR, UV-Vis spectra and elemental analysis. The glass transition temperature and UV-Vis spectra properties of these three organometallic copolymers are found to be different from the normal polystyrene. New synthetic strategy for the synthesis of or-ganometallic copolymer is developed.     

Leaving group effects on the selectivity of the gas-phase fragmentation reactions of side chain fixed-charge-containing peptide ions

The effect of trialkylsulfonium versus quaternaryalkylammonium ions on the multistage gas-phase fragmentation reactions of side chain, fixed-charge, cysteine-containing peptides has been examined in a quadrupole linear ion trap. These tandem mass spectrometry experiments reveal that selective loss of dialkylsulfide from fixed-charge sulfonium ion derivatives is the dominant fragmentation pathway regardless of the degree of proton mobility, indicating that it is the most energetically favored fragmentation pathway. In contrast, the loss of trimethylamine from the side chain of fixed-charge ammonium-ion-containing cysteine derivatives appears to be less energetically favored, and as a result extensive charge-remote fragmentation is observed under low proton mobility conditions, while under conditions of high proton mobility, amide bond fragmentation reactions dominate. These findings are supported by molecular orbital calculations at the B3LYP/6-31 + G(d, p) level of theory, which showed that the neutral loss of dimethylsulfide is both thermodynamically and kinetically preferred over the loss of trimethylamine.     

Photocrosslinkable polymers having p-phenylenediacrylate group in the side chain: Argon laser photoresist

Preparative methods and photosensitivity characteristics of polymers bearing the p-phenylene-diacrylate (PDA) group are described. Condensation of a copolymer of methyl methacrylate and glycidyl methacrylate with p-phenylenediacrylic acid monoester gave highly photosensitive polymers. An alternative method to introduce PDA group is the substitution of chloromethyl-styrene polymer with p-phenylenediacrylic acid monoester monoalkali salt. The latter method was found to be more favorable for preparing soluble photosensitive polymers. The polymers thus prepared showed high sensitivity to light of 488 nm from an Argon laser when sensitizers are used, and the photocrosslinking quantum efficiency was 0.44. Preliminary results on holographic recording with this polymer is also mentioned.     

Adsorbing behavior of polycarboxylate superplasticizer in the presence of the ester group in side chain

The effect of the ester group in side chain on adsorbing behavior and dispersion of polycarboxylate superplasticizer (PC) was studied by comparing the performance of two types of PC. The fluidity of cement paste was tested to discuss the dispersing ability and dispersing retention ability of PC. The total organic carbon analyzer was used to measure the adsorption amount, and the adsorption layer was obtained by x-ray photoelectron spectroscopy. Fourier-transform infrared spectroscopy, nuclear magnetic resonance, and pH value were used to verify the stability of the ester group, and the electrokinetic properties of cement particle were confirmed using the zeta potential measurement. The results show that the ester group in side chain reduces the initial dispersing ability while it increases the dispersing retention ability. The dispersing retention ability depends on the increase of adsorption amount and adsorption layer in 5–60 minutes, and the greater increase leads to the better dispersing retention ability. The ester group can be decomposed to release carboxyl group to enhance the adsorbing ability of PC under the condition of cement hydration, which is the main reason for the greater increase of adsorption amount and adsorption layer and the improvement in dispersing retention ability. It suggests that grafting the ester group is a good way to enhance the dispersing retention ability.     

Inhibition of folylpolyglutamate synthetase by substrate analogues with an ornithine side chain

N^α-[4-[[(4-Aminopteridin-6-yl)methyl]amino]benzoyl]-L-ornithine (dAPA-Orn) was synthesized, and its ability to inhibit folylpolyglutamate synthetase from mouse liver was compared with that of the corresponding 2,4-diamino analogue APA-Orn. Also compared were the inhibitory activities of the deaza analogues 5-deazaAPA-Orn, 8-deazaAPA-Orn, and 5,8-dideazaAPA-Orn, as well as those of N^α-pteroyl-L-ornithine (PteOrn) and its deaza analogues 5-deazaPteOrn and 5,8-dideazaPteOrn. The inhibition constant K_i of dAPA-Orn was 7-fold greater than that of APA-Orn, indicating that the 2-amino group plays a role in binding to the active site. The binding affinity of the 2,4-diamino compounds increased in the order 5-deazaAPA < APA-Orn <5,8-dideazaAPA-Orn < 8-deazaAPA-Orn, and that of the 2-amino-4(3H)-oxo compounds increased in the order 5-deazaPteOrn < PteOrn < 5,8-dideazaPteOrn. The most potent inhibitor of both groups was 8-deazaAPA-Orn, with a K_i of 0.018 μM, coresponding to an 8-fold and 15-fold increase in affinity relative to APA-Orn and 5-deazaAPA-Orn, respectively. The results suggest (a) that the binding of Orn-containing folylpolyglutamate synthetase inhibitors is affected to a greater degree by replacement of N⁸ by a carbon atom than it is by the corresponding change at N⁵, (b) that the effect of carbon for nitrogen replacement is greater in the 2,4-diamino derivatives than in the 2-amino-4(3H)-oxo compounds, and (c) that the 2,4-diamines are the better inhibitors. Comparison of the K_i values of the Orn-containing inhibitors with the K_m values of the corresponding glutamate-containing substrates revealed that K_m/K_i ratio can vary as much as 100-fold depending on the nature of the heterocyclic moiety, suggesting that caution should be exercised in using K_m values of known substrates to predict K_i values of putative inhibitors.     

Synthesis of polyoxiranes and polythiiranes bearing a potential aldehyde group in the side chain

Polyoxiranes and polythiiranes with acetal group in the side chain are prepared by polymerization of 1,1-diethoxy-2,3-epoxy-propane (DEO) and of the corresponding thiirane (DET) using different chiral and achiral initiators. In the case of poly(DET) acetal groups can be removed leading to a polymer with an aldehyde content up to 64 %. In similar experimental conditions the extent of acetal hydrolysis does not exceed 23 % for poly(DEO).