A convenient synthesis of allenes by the reaction of propargyl alcohols with grignard reagents using 1-chloro-2-methyl-n,n-tetramethylenepropenylamine

1-Chloro-2-methyl-N,N-tetramethylenepropenylamine was found to be an efficient condensation reagent for the regioselective coupling reaction of propargyl alcohols with Grignard reagents to give allenes in good yields with high chemo- and enantioselectivities. The utility of the reaction was demonstrated in the stereocontrolled synthesis of methyl (E)-2,4,5-tetradecatrienoate, the pheromone of the male dried bean beetle.     

Synthetic utility of stannyl enolates as radical alkylating agents

[reaction: see text] The radical-initiated beta-ketoalkylation of haloalkanes with tributylstannyl enolates is described. Stannyl enolates derived from aromatic ketones are reactive toward the homolytic beta-ketoalkylation of simple haloalkanes as well as those activated by an electron-withdrawing group. The reactivity of stannyl enolates as radical alkylating agents can be utilized for an efficient three-component coupling reaction among stannyl enolates, haloalkanes, and electron-deficient alkenes.     

Notable deuterium effect on the electron transfer rate of myoglobin

The electron transfer reaction of wild-type myoglobin at an electrode was significantly facilitated in a D2O buffer as compared with that in an H2O buffer, with k(0)'(H2O)/k(0)'(D2O)= 0.13, while a minimal deuterium kinetic isotope effect on the myoglobin with modification at distal histidine (His-64) was observed.     

Kinetics of the radical scavenging activity of beta-carotene-related compounds

To clarify the non-enzymatic radical-scavenging activity of beta-carotene-related compounds and other polyenes, we used differential scanning calorimetry to study the kinetics of radical polymerization of methyl methacrylate (MMA) by 2,2'-azobisisobutyronitrile (AIBN) or benzoyl peroxide (BPO) in the absence or presence of polyenes under nearly anaerobic conditions at 70 degrees C, and analyzed the results with an SAR approach. The polyenes studied were all-trans retinol, retinol palmitate, calciferol, beta-carotene and lycopene. Polyenes produced a small induction period. The stoichiometric factor (n) (i.e. the number of radicals trapped by each inhibitor molecule) of polyenes was close to 0. Tetraterpenes (beta-carotene, lycopene) suppressed significantly more of the initial rate of polymerization (R(inh)) than did diterpenes (retinol, retinol palmitate). The inhibition rate constants (k(inh)) for the reaction of beta-carotene with AIBN- or BPO-derived radicals were determined to be 1.2-1.6x10(5) l/mol s, similar to published values. A linear relationship between (k(inh)) and the kinetic chain length (KCL) for polyenes was observed; as (k(inh)) increased, KCL decreased. KCL also decreased significantly as the number of conjugated double bonds in the polyenes increased. Polyenes, particularly beta-carotene and lycopene, acted as interceptors of growing poly-MMA radicals.     

Sulfur-containing polymers. X. Aromatic poly(sulfenyl thiocarbonates)

Aromatic poly(sulfenyl thiocarbonates) have been synthesized by the interfacial polycondensation of bis(dithiocarbonyl chlorides) with bisphenols. Bisphenols having the hydroxyl groups on separate rings gave polymers in high yields. The inherent viscosities of the polymers ranged from 0.22 to 0.51. In general, they were soluble in chloroform, sym-tetrachloroethane, hexamethylphosphoramide, m-cresol, and dimethylformamide and formed transparent tough films on evaporation of chloroform solutions. Almost all of the polymers were amorphous and gave melt-spun fibers. The polymer films decomposed upon ultraviolet irradiation with liberation of carbonyl sulfide.     

Azetidinic amino acids: stereocontrolled synthesis and pharmacological characterization as ligands for glutamate receptors and transporters

A set of ten azetidinic amino acids, that can be envisioned as C-4 alkyl substituted analogues of trans-2-carboxyazetidine-3-acetic acid (t-CAA) and/or conformationally constrained analogues of (R)- or (S)-glutamic acid (Glu) have been synthesized in a diastereo- and enantiomerically pure form from beta-amino alcohols through a straightforward five step sequence. The key step of this synthesis is an original anionic 4-exo-tet ring closure that forms the azetidine ring upon an intramolecular Michael addition. This reaction was proven to be reversible and to lead to a thermodynamic distribution of two diastereoisomers that were easily separated and converted in two steps into azetidinic amino acids. Azetidines 35-44 were characterized in binding studies on native ionotropic Glu receptors and in functional assays at cloned metabotropic receptors mGluR1, 2 and 4, representing group I, II and III mGlu receptors, respectively. Furthermore, azetidine analogues 35, 36, and 40 were also characterized as potential ligands at the glutamate transporter subtypes EAAT1-3 in the FLIPR Membrane Potential (FMP) assay. The (2R)-azetidines 35, 37, 39, 41 and 43 were inactive in iGlu, mGlu and EAAT assays, whereas a marked change in the pharmacological profile at the iGlu receptors was observed when a methyl group was introduced in the C-4 position, compound 36 versus t-CAA. At EAAT1-3, compound 35 was inactive, whereas azetidines 36 and 40 were both identified as inhibitors and showed selectivity for the EAAT2 subtype.     

Poly(diacetylene)-nanofibers can be fabricated through photo-irradiation using natural polysaccharide schizophyllan as a one-dimensional mold

Schizophyllan interacts with various 1,4-diphenylbutadiyne derivatives to induce their chirally-twisted packing. A series of referential experiments using other polysaccharides (amylose, pullulan, dextran, etc.) and a carbohydrate-appended detergent (dodecyl-beta-d-glucopyranoside) indicates that these 1,4-diphenylbutadiyne derivatives are accommodated within a tubular cavity constructed by a helical superstructure of schizophyllan. In these 1,4-diphenylbutadiyne derivatives, 1,4-bis(p-propionamidophenyl)butadiyne can be easily polymerized through UV-irradiation, in which schizophyllan acts as a one-dimensional mold to produce the corresponding poly(diacetylene)s with fibrous morphologies. Detailed investigations on this unique approach to prepare the nanofibers revealed that it includes two individual processes, that is, 1) UV-mediated polymerization of encapsulated 1,4-bis(p-propionamidophenyl)butadiyne to produce immature nanofibers and 2) their reorganization through hydrophobic interfiber interactions into ordered nanofibers. The other 1,4-diphenylbutadiyne derivatives could not be polymerized through UV-irradiation, indicating that the p-propionamido-functionalities play substantial roles for a suitable packing of the monomer for the polymerization. The other 1,4-diphenylbutadiyne derivatives, however, can be also polymerized through gamma-ray irradiation in the presence of schizophyllan to give the corresponding poly(diacetylene)-nanofibers, emphasizing the wide applicability of the schizophyllan-based strategy for polymerization of various 1,4-diphenylbutadiyne derivatives.