Chemical synthesis of 23 kDa glycoprotein by repetitive segment condensation: a synthesis of MUC2 basal motif carrying multiple O-GalNAc moieties

Peptide thioester corresponding to a MUC2 tandem repeat unit, which retains seven GalNAc moieties, was prepared by the Fmoc method followed by the low TfOH treatment to remove benzyl groups at the carbohydrate portions. The glycosylated peptide thioester was then consecutively joined by the activation of a thioester group by silver ions to obtain a MUC2 tandem repeat model composed of 141 amino acids with 42 GalNAc moieties.     

Preparation of Polylactide Microspheres Having Positively or Negatively Charged Surfaces

The syntheses of polylactides (PLAs) with branched peptide end groups containing reactive (ionic) moieties such as amino or carboxyl groups are described and were used to prepare PLA‐based microspheres (MSs) with positively or negatively charged surfaces. Branched peptides with hydroxyl end groups and four protected amino or carboxyl groups, Boc₄‐K₃‐OH or Bn₄‐E₃‐OH, were synthesized, and the hydroxyl group converted to an alkoxide and was used as the initiation site for the ring‐opening polymerization of L ‐lactide. Subsequent deprotection gave PLAs end‐capped with branched peptides having four amino or carboxyl groups, respectively (K₃‐PLA and E₃‐PLA). K₃‐PLA and E₃‐PLA were converted to K₃⁴⁺‐PLA and E₃^4?‐PLA by acid or base treatment, respectively. MSs with charged surfaces were then prepared using K₃⁴⁺‐PLA or E₃^4?‐PLA as a surfactant [MS(K₃⁴⁺‐PLA) or MS(E₃^4?‐PLA)]. The ionic surface state of the MSs was confirmed by colloidal titration and zeta potential analysis.

SEM image of MSs: MS(K₃⁴⁺‐PLA).     

Formation of n-alkyl-n(1-hydroperoxyalkyl)nitrosamines from n-alkyl-n-(1-acetoxyalkyl)nitrosamines

N-alkyl-N-(1-hydroperoxyalkyl)nitrosamines were prepared by treatment of the corresponding 1-acetoxyalkyl nitrosamines with hydrogen peroxide in acetic acid through an acid-catalyzed nucleophilic substitution.     

Synthesis of a Tricyclic Bisguanidine Compound Structurally Related to Saxitoxin and its Identification in Paralytic Shellfish Toxin‐Producing Microorganisms

We recently reported the chemical synthesis and identification of the genetically predicted biosynthetic intermediates of saxitoxin (STX), including a 2‐aminoimidazole‐bearing monoguanidine compound (Int‐C′2) in two paralytic shellfish toxin (PST)‐producing microorganisms. In this study, we achieved the direct conversion of Int‐C′2 into a tricyclic bisguanidine compound (called Cyclic‐C′), which is structurally related to STX, through oxidative intramolecular guanidine transfer to 2‐aminoimidazole catalyzed by Pd/C under basic conditions in air. By using HPLC‐MS analysis, Cyclic‐C′ was also identified in the PST‐producing microorganisms, suggesting that Cyclic‐C′ is either another biosynthetic intermediate or a shunt product of PSTs. In addition, a weak inhibitory activity of Cyclic‐C′ to the voltage‐gated sodium channels was detected by using a cell‐based assay.     

Rhodium/chiral diene-catalyzed asymmetric methylation of N-sulfonylarylimines with trimethylboroxine

A hydroxorhodium complex coordinated with a chiral diene ligand catalyzed the asymmetric addition of trimethylboroxine to N-sulfonylarylimines to give high yields of chiral 1-aryl-1-ethylamines with high enantioselectivity.     

Cyclic Acetal-Photosensitized Polymerization. IV. Photopolymerization of Styrene in the Presence of 1, 3:2, 4:5, 6-Trimethylene-D-Sorbitol

Styrene(St) was polymerized in benzene solution in the presence of l, 3:2, 4:5, 6-trimethylene-D-sorbitol(TCA) by means of photo-irradiation of system at 30°C. It was found that the polymerization was depressed by the addition of TCA and then proceeded through a radical mechanism. The chain-transfer constant of the styryl radical to TCA was estimated to be 0.16. Accordingly, the photopolymerization of St in the presence of TCA is studied kinetically with regard to chain transfer and termination.     

Syntheses of 5-Fluorouracil-Terminated Monomethqxypqly(Ethylene Glycol)S,Their Hydrolysis Behavior,and Their Antitumor Activities

The covalent attachments of 5-fluorouracil (5FU) units to poly(ethylene glycol) monomethoxy ether (MeO-PEG) attached through ester, amide, and ether bonds were carried out; three types of linkages were obtained through which 5FU units were attached to MeO-PEG. For the investigation of the release of the 5FU units, the homogeneous hydrolysis was investigated in vitro in the presence and absence of enzymes. Although the rate of release of l-β-carboxyethyl-5FU or 1-β-hydroxyethyl-5FU from the compounds was fast, the release of 5FU itself was slow. In addition, the antitumor activity of these three types of MeO-PEG-bound 5FU unit was tested in vivo by preliminary screening by the National Cancer Institute or by the Japanese Foundation for Cancer Research.