Lup-15-en-3β-ol, acetate

A small library of degradable polyester-like glycopolymers was successfully prepared by the combination of radical ring-opening copolymerization of 2-methylene-1,3-dioxepane as a cyclic ketene acetal (CKA) with vinyl ether (VE) derivatives and a Pd-catalyzed thioglycoconjugation. The resulting thioglycopolymers were formulated into self-stabilized thioglyconanoparticles, which were stable up to 4 months and were enzymatically degraded. Nanoparticles and their degradation products exhibited a good cytocompatibility on two healthy cell lines. Interactions between thioglyconanoparticles and lectins were investigated and highlighted the presence of both specific carbohydrate/lectin interactions and nonspecific hydrophobic interactions. Fluorescent thioglyconanoparticles were also prepared either by encapsulation of Nile red or by the functionalization of the polymer backbone with rhodamine B. Such nanoparticles were used to prove the cell internalization of the thioglyconanoparticles by lung adenocarcinoma (A549) cells, which underlined the great potential of P(CKA-co-VE) copolymers for biomedical applications.

Two hexoses and two pentoses have been reacted with two equivalents of trichloroacetaldehyde using boron trifluoride etherate as promoter in dioxane at reflux. The major products are exo-1,2-O-trichloroethylidenealdofuranoses in every case in varying yields, identical to the products previously obtained in lower yields using sulfuric acid or hydrochloric acid as promoter in trichloroacetaldehyde as solvent. Careful fractionation of the remainders of the product mixtures showed that the other isomer in the acetal ring was also produced in most cases but small amounts of the two 1,2-O-trichloroethylidenealdopyranose isomers were also produced. In addition, very small amounts of other products were identified that were derived from boron trifluoride etherate and the solvent. A mechanism involving rate-determining acetal ring closure was proposed to explain the formation of furanose derivatives, rather than pyranose derivatives. Methods for removal of the trichloroethylidene acetals were investigated for substituted derivatives and it was found that a process involving reduction with tributyltin hydride was effective.

In this report, we demonstrate that visible light photoactivation of 6-bromo-2-naphthol facilitates the photoacid-catalyzed acetalization of carbonyls with alcohols. We also demonstrate that 2-naphthol when coupled to a photosensitizer provides acetals from electron-deficient aldehydes. In addition, the S1 excited state pKa for 6-bromo-2-naphthol in water was determined and shown to have increased excited-state acidity relative to 2-naphthol.