Post-synthetic modification of oligonucleotides containing 5-trifluoromethylpyrimidine bases

A practical and operationally simple post-synthetic modification of oligonucleotides containing 5-trifluoromethylpyrimidine bases is described. Trifluoromethyl group was used as a post-synthetic precursor and 5-trifluoromethylpyrimidine bases within oligonucleotides were converted into the corresponding 5-carboxy-, 5-cyano-, 5-amidinyl-, and 5-carbamoyl derivatives by treatment with an alkaline solution and amines. Moreover, post-synthetic treatment of fully protected and controlled pore glass (CPG)-attached oligonucleotides proceeded successfully with the simultaneous removal of all protecting groups, cleavage from CPG, and conversion of the trifluoromethyl group to afford the corresponding modified oligonucleotides.     

Mechanical denaturation of high polymers in solutions

Summary First, the effect of micro-gels, which formed in the aqueous solution of syndiotacticity-rich PVA(s-PVA) of higher molecular weight under quiescence, on the flow-induced crystallization was examined. The gel panicles which formed under quiescence did not play a role as seed crystals for the flow-induced crystallization. Second, for s-PVA of lower molecular weight, the productions of particles under quiescence and flow in the aqueous solutions were compared.cf. part XXXVI. K. Yamaura, Y. Okumura, S. Matsuzawa, J. Macromol. Sci.(-Phys.), in press.Dedicated to Professor Dr. K. Ueberreiter on his 70th birthday.     

Enantioselective Synthesis of 1,2-Benzothiazine 1-Imines via RuII/Chiral Carboxylic Acid-Catalyzed C−H Alkylation/Cyclization

Sulfondiimines are diaza-analogues of sulfones with a chiral sulfur center. Compared to sulfones and sulfoximines, their synthesis and transformations have so far been studied to a lesser extent. Here, we report the enantioselective synthesis of 1,2-benzothiazine 1-imines, i.e., cyclic sulfondiimine derivatives from sulfondiimines and sulfoxonium ylides via C−H alkylation/cyclization reactions. The combination of [Ru(p-cymene)Cl₂]₂ and a newly developed chiral spiro carboxylic acid is key to achieving high enantioselectivity.     

Discovery of New Cytotoxic Aplaminone Derivatives from the Sea Hare Aplysia kurodai and Elucidation of Their Accumulation from Local Sea Algae through the Food Chain

The shell-less herbivorous marine mollusk (sea hare) Aplysia kurodai is known to contain a variety of bioactive substances. While these compounds have been thought to originate from sea algae or their associated microbes, most of their origin and acquisition pathways are still unclear. Six new cytotoxic aplaminone derivatives, bromodopamine-terpenoid hybrid molecules, were isolated from A. kurodai. Among them, isoaplaminone had a reverse prenyl group at the C15 aliphatic chain, which is a rare structural feature from the viewpoint of terpenoid biosynthesis. Investigation for chemical components in A. kurodai and the sea algae collected at several different locations revealed that two major aplaminones were contained in the Laurencia complex species at specific sites. Our chemical and ecological studies provide new insights into the origin of marine alkaloid toxins and their dynamism through the food chain.     

Trajectory of the spectral/structural rearrangements for photo-oxidative reaction of neat ketoprofen and its cyclodextrin complex

Journal of Inclusion Phenomena and Macrocyclic Chemistry - Ketoprofen is a nonsteroidal anti-inflammatory drug used as mohrus tape which causes unwanted photosensitivity due to UV irradiation. In...     

Synthesis of Furoxans (1,2,5‐oxadiazole 2‐oxides) from Styrenes and Nitrosonium Tetrafluoroborate in Non‐Acidic Media and Mechanistic Study

Diverse furoxans (1,2,5‐oxadiazole 2‐oxides) were synthesized from the corresponding styrenes using nitrosonium tetrafluoroborate as the nitrosation reagent in pyridine (basic media) or dichloromethane (neutral media). Acid‐sensitive functional groups were tolerated under these conditions. The probable reaction mechanism was elucidated. The experimental results support an ionic reaction pathway in contrast to the conventional acidic conditions with a radical mechanism.     

Total Synthesis and Complete Stereostructure of a Marine Macrolide Glycoside, (−)‐Lyngbyaloside B

We have described in detail the total synthesis of both the proposed and correct structures of (?)‐lyngbyaloside B, which facilitated the elucidation of the complete stereostructure of this natural product. Our study began with the total synthesis of 13‐demethyllyngbyaloside B, in which an esterification/ring‐closing metathesis (RCM) strategy was successfully used for the efficient construction of the macrocycle. We also established reliable methods for the introduction of the conjugated diene side chain and the l ‐rhamnose residue onto the macrocyclic framework. However, the esterification/RCM strategy proved ineffective for the parent natural product because of the difficulties in acylating the sterically encumbered C‐13 tertiary alcohol; macrolactionization of a seco‐acid was also extensively investigated under various conditions without success. We finally completed the total synthesis of the proposed structure of (?)‐lyngbyaloside B by means of a macrolactonization that involves an acyl ketene as the reactive species. However, the NMR spectroscopic data of our synthetic material did not match those of the authentic material, which indicated that the proposed structure must be re‐examined. Inspection of the NMR spectroscopic data of the natural product and molecular mechanics calculations led us to postulate that the configuration of the C‐10, C‐11, and C‐13 stereogenic centers had been incorrectly assigned in the proposed structure. Finally, our revised structure of (?)‐lyngbyaloside B was unambiguously verified through total synthesis.