Total synthesis of mannosyl tryptophan and its derivatives

Glycosylation is one of the most important post- or co-translational modifications of proteins, which affects the biological activities of the parent proteins by influencing the higher-order structure. Recently, a highly novel variant of glycoproteins that incorporate a C-glycosylated amino acid was identified in various proteins. The total synthesis of one such C-glycosyl amino acid, namely, C (2)-alpha-D-C-mannosylpyranosyl-L-tryptophan and related peptides were successfully achieved. The mannose and tryptophan moieties were connected via ring opening of benzyl-protected 1,2-anhydro-mannose by a lithiated indole derivative. After the functional group conversion and deprotection steps, the glyco-amino acid was synthesized in a concise and stereoselective manner, in high overall yields. The stereoisomer, C (2)-alpha-D-C-glycosylpyranosyl-L-tryptophan was synthesized in a similar way. Furthermore, it was revealed that the intermediate azido acid can serve as a useful building block for peptide elongation. A synthetic route for the peptide bond formation of a glycopeptide, without protection of the hydroxyl groups, using the triazine salt derivative as a coupling reagent is also reported.     

Foaming properties of monoglycerol fatty acid esters in nonpolar oil systems

Foaming properties of monoglycerol fatty acid esters that have different alkyl chain lengths were studied in different nonpolar oils, namely liquid paraffin (LP 70), squalane, and squalene. The effect of the hydrocarbon chain length of the surfactant, the concentration, the nature of the oil, and the temperature on the nonaqueous foam stability was mainly studied. Five weight percent of glycerol alpha-monododecanoate (monolaurin) formed highly stable foams in squalane at 25 degrees C, and the foams were stable for more than 14 h. Foam stability of the monolaurin/LP 70 and the monolaurin/squalene systems are almost similar, and the foams were stable for more than 12 h. Foam stability was decreased as the hydrocarbon chain length of the monoglyceride decreased. In the glycerol alpha-monodecanoate (monocaprin)-oil systems, the foams were stable only for 3-4 h, depending on the nature of the oil. However, the foams formed in the glycerol alpha-monooctanoate (monocaprylin)-oil systems coarsened very quickly, leading to the progressive destruction of foam films, and all of the foams collapsed within a few minutes. Foam stability decreased when the oil was changed from squalane to squalene, in both monocaprin and monolaurin systems. It was observed that, in the dilute regions, these monoglycerides form fine solid dispersions in the aforementioned oils at 25 degrees C. At higher temperatures, the solid melts to isotropic single-liquid or two-liquid phases and the foams formed collapsed within 5 min. Judging from the wide-angle X-ray scattering (WAXS) and the foaming test, it is concluded that the stable foams are mainly caused by the dispersion of the surfactant solids (beta-crystal) and foam stability is largely influenced by the shape and size of the dispersed solid particles.     

Successful preferential formation of a novel macromolecular assembly--trilayered polymeric micelle--that can incorporate hydrophilic compounds: the optimization of factors affecting the micelle formation from amphiphilic block copolymers

We have developed a novel macromolecular assembly, trilayered polymeric micelle, which can incorporate hydrophilic compounds. The micelle can be prepared from the amphiphilic block copolymers without regard to their properties such as the copolymer's charges and the homogeneity of the copolymers forming the micelle's inner and outer parts. In this study, we investigated the optimal condition for the preferential formation of the trilayered polymeric micelle. GPC results clarified that the composition of the block copolymer, the concentration of PVA in the aqueous bulk phase, and the temperature during the preparation were the important preparation factors affecting preferential formation of the trilayered polymeric micelles. We successfully achieved the preferential formation of the trilayered polymeric micelles under optimal conditions. Furthermore, we confirmed that the model hydrophilic compound, FITC-dextran, was successfully encapsulated into the hydrophilic core of the trilayered polymeric micelles. The novel micelle that can incorporate hydrophilic compounds can have a variety of future medical applications such as a protein delivery-based therapy.     

Synthesis and properties of new block copolymers based on poly(ether sulfone) and aramids

New poly(ether sulfone)–aramid block copolymers were synthesized from an α, ω-diamineterminated poly(ether sulfone) oligomer, aromatic diamines, and aromatic dicarboxylic acid chlorides by the low-temperature solution polycondensation in N-methyl-2-pyrrolidone. By the introduction of aramid into the poly(ether sulfone), the glass transition temperatures of the block copolymers rose and the mechanical properties were significantly improved. Microphase separation, which often takes place in many block copolymers, did not occur in the present block copolymers. © 1993 John Wiley & Sons, Inc.     

Silafunctional Compounds in Organic Synthesis. XXXVII. Metalated (Allyl) Aminosilanes: Regioselective Coupling with Alkyl Halides to (E)-1-Alkenylsilanes with a Functional Group on Silicon

(E)-1-Alkenylsilanes with an amino or an alkoxy group on silicon can be conveniently synthesized by regioselective coupling of a potassium reagent derived from an allyl(amino)silane with alkyl halides.     

Gold(I)‐Catalyzed Cascade Cyclization Reactions of Allenynes for the Synthesis of Fused Cyclopropanes and Acenaphthenes

A gold‐catalyzed reaction of phenylene‐tethered allenynes with benzofurans gave 1‐(naphth‐1‐yl)cyclopropa[b]benzofuran derivatives, whereas the reaction of 1‐allenyl‐2‐ethynyl‐3‐methylbenzene derivatives in the absence of benzofurans gave acenaphthenes in good yields. These results can be rationalized by nucleophilic attack of the alkyne moiety on an activated allene to form a vinyl cation intermediate.     

Synthesis and fluorescent properties of conjugated copolymers containing maleimide and fluorene units at the main chain

Yamamoto or Suzuki–Miyaura coupling polymerizations of 2,3‐diiodo‐N‐cyclohexylmaleimide with fluorene derivatives (2,7‐dibromo‐9,9′‐dihexylfluorene and 9,9′‐dihexylfluorene‐2,7‐diboronic acid) were carried out. The number‐average molecular weights (M_n) of the resulting copolymers were 2600–3500 by gel permeation chromatography analysis. The fluorescence emission of the alternating copolymer showed the emission maxima at 551 nm in THF. On the other hand, the random copolymers showed the bimodal emission peaks at 418–420 and 555–557 nm region, respectively. The fluorescence peaks of the random copolymers on the long wavelength region (555–557 nm) were attributed to the conjugated neighboring N‐cyclohexylmaleimide‐9,9′‐dihexylfluorene units in the polymer main chain. Furthermore, the copolymers exhibited the fluorescence solvatochromism by the difference of the polarity of solvents. The alternating and random copolymers showed the different fluorescence solvatochromism, and the emission colors are distinguishable by the naked eye, respectively. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4945–4956     

Synthesis and Polymerization of Optically Active Mono-I-Menthyl Itaconate

Optically active mono-l-menthyl itaconate (MMI) was prepared from ita-conic acid and l-menthol. MMI was polymerized in bulk at 80°C to give a chiral homopolymer having -49.5° specific rotation. MMI (M₁ was copolymerized with styrene (ST, M₂), methyl methacrylate (MMA, M₂), and N-cyclohexylmaleimide (CHMI, M₂) by using 2,2′-azobisisobutyronitrile (AIBN) as the radical initiator and benzene as the polymerization solvent at 50°C. The monomer reactivity ratios (r₁, r₂) and Alfrey-Price Q, e values were determined to be r₁ = 0.28, r₂ = 0.32, Q₁ = 0.90, and e₁ = 0.75 in MMI-ST; r₁ = 0.09 and r₂ = 0.51 in MMI-MMA; and r₁ = 0.78 and r₂ = 0.39 in MMI-CHMI. The chiroptical properties of the polymers were investigated.     

Orientational anisotropy of bead-spring star chains during creep process

The bead-spring model for star chains (Rouse–Ham model) is a fundamental model for the polymer dynamics. Despite the importance of this model, its dynamics under the stress-controlled condition was not analyzed so far. For completeness of the model, the equation of motion of the Rouse–Ham chain was solved to derive an analytical expression of the orientation function S(n,t) for the stress-controlled creep process. This expression indicated that the segments near the free end of the star arm exhibit overshoot of their orientational anisotropy to compensate for the slow growth of the anisotropy near the branching point and that the distribution of the anisotropy along the arm contour becomes more heterogeneous with increasing arm number f. This correlation/interplay of the segments at different locations along the arm, not seen under the strain-controlled condition, is a natural consequence of the constant-stress requirement during the creep process. The corresponding interplay was noted also for respective Rouse–Ham eigenmodes. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3501–3517, 2006