Polymerization of N-carboxy-amino acid anhydrides in the solid state. I. Polymerizability of the various α-amino acid NCAs in the solid state

The solid-state polymerization of various α-amino acid NCAs was investigated and the results were compared with those obtained by heterogeneous polymerization in acetonitrile. Essential differences were found in the polymerizability of the NCAs in these two systems. In the solid state, L-leucine NCA was the most reactive among the NCAs examined, and its reactivity was even higher than in the precipitation polymerization of acetonitrile solutions. On the other hand, glycine NCA was the most inert among the NCAs examined in the solid state. The difference between the reactivities of glycine NCA and L-alanine NCA was interpreted in terms of their crystal structures. Several kinetic features of the solid-state polymerization were studied on γ-benzyl-L -glutamate NCA.     

Four-center type photopolymerization in the solid state. IV. Polymerization of α,α′-dicyano-p-benzenediacrylic acid its derivatives

The solid-state photopolymerization of α,α′-dicyano-p-benzene diacrylic acid (p-CBA) series has been studied. p-CBA, its esters, amide, and a few other cyano derivatives were prepared and new polymers were obtained from p-CBA alkyl esters on irradiation of ultraviolet or visible light. Though the polymerization behavior differs with each monomer, polymerization proceeds in essentially the same manner as in the 2,5-distyrylpyrazine (DSP) and p-benzenediacrylic acid (BDA) series: the reaction proceeds topochemically forming polymer with a cyclobutane ring in the main chain. Properties of high polymer are typical of cyclobutane-containing polymer. That is, they are highly crystalline with high melting temperature and a limited solubility. The study on this series of compounds, as well as the DSP and p-BDA series, supports the generalization that solid-state dimerization can be extended to solid-state photopolymerization of compound having two dimerizable units in a molecule.     

Electron spin resonance study of γ-irradiated poly(methacrylic acid)

Low temperature relaxations in poly(methacrylic acid) (PMAA) have been studied by electron spin resonance (ESR) spectroscopy. The observed 8 line ESR spectra of irradiated PMAA in the temperature range 77-300K (LNT-RT) is attributed to the free radicals of the type ～ CH₂? CH? CH₃. Assignment of ESR spectra to free radicals has been made on the basis of magnetic parameters employed to simulate ESR spectra at different temperatures. Further, ESR spectra below LNT have been simulated, using the set of parameters employed to simulate the experimental spectrum at LNT. Magnetic parameters of the ESR spectra at LNT and below LNT indicate γ- and δ-relaxations of PMMA chains. © 1994 John Wiley & Sons, Inc.     

Kinetics of the γ-radiation-induced polymerization of methyl methacrylate in the solid state

Studies have been made of the γ-radiation-induced polymerization of methyl methacrylate in bulk, in the solid state at a temperature of ?65°C. and a radiation intensity of 346,000 rad/hr. The reaction was found to have an extremely long induction period (～50 hr.) when pure monomer was used, and to be first-order with respect to polymer concentration. This first-order dependency was confirmed by a series of irradiations in which 0.6% poly(methyl methacrylate) was dissolved in the monomer before irradiation. These irradiations showed no induction period. Nuclear magnetic resonance spectroscopy indicated a much more heterotactic polymer than that obtained in the liquid state at ?49°C.     

Thermal degradation in the solid state of metal salts of methacrylic acid oligomers

Alkaline earth metal salts of methacrylic acid oligomers undergo thermal degradation at 450–500°C to yield five-membered ring cyclic ketones. Some detailed studies are described in this paper. Magnesium 1-hexene-2,5-dicarboxylate undergoes thermal tetramerization in the solid state at temperatures above 300°C, but below the temperature of decomposition of the salt, to give two tetramers, 4-dodecene-2,5,8,11-tetracarboxylate and 5-dodecene-2,5,8,11-tetracarboxylate. At 450–500°C, the tetramers are converted to 1-(3-methyl-2-oxocyclopent-3-enyl)-2-(3-methyl-2-oxocyclopentyl)ethane, which, in turn, decomposes into two cyclic ketones,2,5-dimethylcyclopentan-1-one and 2,5-dimethylcyclopent-3-en-1-one. Trimer salt, magnesium 1-nonene-2,5,8-tricarboxylate, is difficult to thermally hexamerize in the solid state and, rather, decomposes at 450–500°C directly into 3,8-dimethylbicyclo[4,3,0]-nonen-2,7-dione, which yields a mixture of three ketones, 2-methylcyclopentan-1-one, 2,5-dimethylcyclopentan-1-one and 2,5-dimethylcyclopent-3-en-1-one.     

Solid‐state conformations of linear depsipeptide amides with an alternating sequence of α,α‐disubstituted α‐amino acid and α‐hydroxy acid

Depsipeptides and cyclodepsipeptides are analogues of the corresponding peptides in which one or more amide groups are replaced by ester functions. Reports of crystal structures of linear depsipeptides are rare. The crystal structures and conformational analyses of four depsipeptides with an alternating sequence of an α,α‐disubstituted α‐amino acid and an α‐hydroxy acid are reported. The molecules in the linear hexadepsipeptide amide in (S)‐Pms‐Acp‐(S)‐Pms‐Acp‐(S)‐Pms‐Acp‐NMe₂ acetonitrile solvate, C₄₇H₅₈N₄O₉·C₂H₃N, ( 3b ), as well as in the related linear tetradepsipeptide amide (S)‐Pms‐Aib‐(S)‐Pms‐Aib‐NMe₂, C₂₈H₃₇N₃O₆, ( 5a ), the diastereoisomeric mixture (S,R)‐Pms‐Acp‐(R,S)‐Pms‐Acp‐NMe₂/(R,S)‐Pms‐Acp‐(R,S)‐Pms‐Acp‐NMe₂ (1:1), C₃₂H₄₁N₃O₆, ( 5b ), and (R,S)‐Mns‐Acp‐(S,R)‐Mns‐Acp‐NMe₂, C₃₀H₃₇N₃O₆, ( 5c ) (Pms is phenyllactic acid, Acp is 1‐aminocyclopentanecarboxylic acid and Mns is mandelic acid), generally adopt a β‐turn conformation in the solid state, which is stabilized by intramolecular N—H…O hydrogen bonds. Whereas β‐turns of type I (or I′) are formed in the cases of ( 3b ), ( 5a ) and ( 5b ), which contain phenyllactic acid, the torsion angles for ( 5c ), which incorporates mandelic acid, indicate a β‐turn in between type I and type III. Intermolecular N—H…O and O—H…O hydrogen bonds link the molecules of ( 3a ) and ( 5b ) into extended chains, and those of ( 5a ) and ( 5c ) into two‐dimensional networks.     

γ–α Solid–solid transition of isotactic polypropylene

X-ray diffraction patterns have been taken as a function of time and temperature on a sample of polypropylene held under high pressure (4.14 kbar) for 180 hr. at a temperature of 248°C. and subsequently cooled to room temperature. The molded sample initially crystallizes in the triclinic γ–phase but transforms to the γ–phase at elevated temperatures. The rate of conversion from γ to α is a function of time and temperature and tends to approach a constant value with increasing time. The nature of the thermal changes occurring in the sample was also studied by differential scanning calorimetry. It appears that at low scan speeds, there is a solid–solid transformation from the α-phase to the γ–phase, but at high scan speeds, the γ–phase melts without conversion to the α-phase.     

The synthesis of β-heteroarylamino-α,β-dehydro-α-amino acid and β-heteroarylamino-α-amino acid derivatives

From heteroarylaminomethyleneoxazolones 4 , obtained from N-heteroarylformamidines 2 and 2-phenyl-5-oxo-4,5-dihydro-1,3-oxazole ( 3 ), the following β-heteroarylamino-α,β-dehydro-α-amino acid derivatives were prepared: methyl 8 and ethyl esters 9 , amides 10 and 11 , hydrazides 12 , and azides 15 . By catalytic hydrogenation the compounds 4 were converted into β-heteroarylamino substituted amides 18 and β-heteroarylamino-α-amino acids 20 .     

Synthesis and isolation of chloro‐β‐carbolines obtained by chlorination of β‐carboline alkaloids in solution and in solid state

β‐Carbolines (1‐5) undergo electrophilic aromatic substitution with N‐chlorosuccinimide and N‐chlorobenzotriazole under different experimental conditions. Although 6‐chloro and 8‐chloro‐nor‐har‐mane ( 1a and 1b ) and 6‐chloro and 8‐chloro‐harmane ( 2a and 2b ) obtained by chlorination with sodium hypochlorite of nor‐harmane (1) and harmane (2) were isolated and fully characterized recently, other chloroderivatives of nor‐harmane and harmane have never been described. The preparation and subsequent isolation, purification and full characterization of the dichloroderivatives 1c and 2c are reported (mp, R_f, ¹H nmr, ¹³C nmr and ms) together with the preparation, isolation and charaterization, for the first time, of the chloroderivatives obtained from harmine (3a‐3c) , harmol (4a‐4b) and 7‐acetylharmol (5a‐5c) . As chlorinating reagent N‐chlorosuccinimide and N‐chlorobenzotriazole in solution as well as the β‐carboline ‐N‐chlorosuccinimide solid mixture have been used and their uses have been compared. Gc (t_R) and gc‐ms (m/z) data for other monochloro derivative of nor‐harmane (1d) and monochloro‐ and dichloroderivatives of harmane ( 2d and 2e‐2f ), obtained in trace amounts, are also included (Scheme 1 and Table I). Semiempirical AM1 and PM3 calculations have been performed in order to predict reactivity in terms of the energies of HOMO‐LUMO difference and in terms of the charge density of β‐carbolines (1‐5) and chloro‐β‐carbolines ( 1a‐1c, 2a‐2c, 3a‐3c, 4a‐4b , and 5a‐5c ) (Scheme 1). Theoretical and experimental results are discussed briefly.     

High-performance liquid chromatographic method for the separation of the optical isomers of γ,γ′-di-tert.-butyl- -γ-carboxyglutamic acid and -γ-carboxyglutamic acid

The chemical synthesis of γ,γ′-tert.-butyl-γ-carboxyglutamic acid is accompanied by extensive racemization, and very careful resolution is needed to obtain and -γ,γ′-di-tert.-butyl-γ-carboxyglutamic acids in high chiral purity. A novel method was devised for the separation of enantiomers of γ,γ′-di-tert.-butyl-γ-carboxyglutamic acid and γ-carboxyglutamic acid, applying precolumn derivatization with 1-fluoro-2,4-dinitrophenyl-5- -alanine amide and 2,3,4,6-tetra-O-acetyl-β- -glucopyranosyl isothiocyanate as chiral reagents, with subsequent reversed-phase high-performance liquid chromatographic separation of diastereomeric compounds. The effects of organic modifiers, of the mobile-phase composition and of the pH on the separation of the diastereomers were investigated.     

Chemical synthesis of poly‐γ‐glutamic acid by polycondensation of γ‐glutamic acid dimer: Synthesis and reaction of poly‐γ‐glutamic acid methyl ester

α‐Methyl glutamic acid (L ‐L )‐, (L ‐D )‐, (D ‐L )‐, and (D ‐D )‐γ‐dimers were synthesized from L ‐ and D ‐glutamic acids, and the obtained dimers were subjected to polycondensation with 1‐(3‐dimethylaminopropyl)‐3‐ethylcarbodiimide hydrochloride and 1‐hydroxybenzotriazole hydrate as condensation reagents. Poly‐γ‐glutamic acid (γ‐PGA) methyl ester with the number‐average molecular weights of 5000∼20,000 were obtained by polycondensation in N,N‐dimethylformamide in 44∼91% yields. The polycondensation of (L ‐L )‐ and (D ‐D )‐dimers afforded the polymers with much larger |[α]_D | compared with the corresponding dimers. The polymer could be transformed into γ‐PGA by alkaline hydrolysis or transesterification into α‐benzyl ester followed by hydrogenation. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 732–741, 2001     

Solid-state polymerization studies. I. 2-vinylnaphthalene post-polymerization initiated by 60Co γ-irradiation

⁶⁰Co γ-irradiated 2-vinylnaphthalene was obsreved to post-polymerize in the solid phase. Plots of conversion versus time indicated a 14% limiting conversion of monomer to polymer. The post-polymerization was found to be first-order in monomer with an Arrhenius activation energy of 19.0 kcal./mole.     

Synthesis of γγγ-trifluorocarbonyl compounds

γγγ-Trifluorocarbonyl compounds are easily obtained in a good yield by introduction of the 1,1,1-trifluoroethyl moiety (CF₃-CH₂-) on the -methylene group of a ketone.     

3β‐Acetoxy‐5α,6β‐di­hydroxybisnorcholanic acid 2216 lactone

In the title compound, C₂₄H₃₆O₆, the ester linkage in ring A is equatorial. The six‐membered rings A, B and C have chair conformations. The five‐membered ring D adopts a 13β,14α‐half‐chair conformation and the E ring adopts an envelope conformation. The A/B, B/C and C/D ring junctions are trans, whereas the D/E junction is cis.     

Molecular weight distributions in radiation-induced polymerization. VI. γ-ray-induced polymerization of “dry” styrene in the solid state

The γ-ray-initiated polymerization of styrene in the solid state has been studied over the temperature range ?35°C to ?55°C for samples exhaustively purified and dried to remove residual water (“dry” samples). Comparison with kinetic results previously reported for dry samples in the liquid state indicates a sharp decrease in the rate of polymerization resulting from the liquid to solid state transition. The molecular weight distributions for in-source polymerization at ?35°C and ?40°C are bimodal in nature, and the appearance of a third peak is noticeable at ?47°C and ?55°C. In the case of postpolymerization at ?35°C the molecular weight distribution is bimodal as in the case of in-source samples. In the former case, however, the high molecular weight peak is predominant whereas the low molecular weight peak predominates in the latter. These results have been tentatively attributed to the postulated coexistence of two distinct propagating species which are radical and cationic in nature.