Synthesis of Urea‐Tethered Disaccharides in Water

A new method for the synthesis of urea‐linked disaccharides in aqueous media has been developed. The key feature of our approach is two strained Steyermark‐type gluco‐ and galactopyranosyl oxazolidinones. Each oxazolidinone is attached to a pyranose ring in a di‐equatorial trans‐annulation framework. Reaction of these oxazolidinones with 4‐aminohexopyranose in water proceeded smoothly to afford the urea‐tethered cellobiose and lactose analogues. The galactose‐type oxazolidinone proved to be more reactive than the glucose‐type, which is explained by the presence of an axial hydroxy group at C4 in the former.     

Analyses of structure of photoreceptor organelle and blepharismin-associated protein in unicellular eukaryote Blepharisma

In the ciliated protozoan Blepharisma, step-up photophobic response is believed to be mediated by a novel type of photosensory pigment known as "blepharismins" (BL) that are contained in the pigment granules located just beneath the plasma membrane. We examined the ultrastructure of the pigment granules by freeze-fracture and thin-section electron microscopy and proposed a schematic diagram showing the granules' three-dimensional inner membranous structure. Some of the BL are suggested to be associated with 200 kDa membrane protein. High-pressure liquid chromatography analysis of pigment species associated with 200 kDa protein obtained from blue forms of Blepharisma (oxyblepharisma) revealed that the 200 kDa protein was associated with five types of oxyblepharismin. The fluorescence intensity was increased when the pigments were dissociated from the 200 kDa protein. The result supports the hypothesis that the pigment-200 kDa complex is able to transduce light energy into signals mediating the photobehavior of Blepharisma.     

Photosensitized oxygenation of phenylpyruvic acid derivatives as a model for p-hydroxyphenylpyruvate dioxygenase

Dye-sensitized photooxygenation of enol ethers of methyl phenylpyruvates ($\text{3}$) produced diendoperoxides $\text{4}$ in aprotic solvents, whereas in methanol hydroxylated product $\text{6}$ was obtained. The reaction scheme is discussed in comparison uith that for the enzymic transformation.     

Unprecedented hydrothermal reaction of o-phenylaniline and related derivatives with cyclic ketones. A novel approach to the construction of phenanthridine and quinoline ring systems

[reaction: see text] A new method for synthesizing phenanthridine and its related compounds was developed using the condensation of o-phenylaniline and its homologues with cyclic ketones under hydrothermal conditions.     

Pd(II)-catalyzed acetal/ketal hydrolysis/exchange reactions

PdCl₂(CH₃CN)₂ catalyzes the hydrolysis of dioxolane acetals and ketals in moist CH₃CN, while in acetoze, efficient and more reproducible exchange reactions take place.     

High pressure organic chemistry; XV. Non-catalyzed cleavage reaction of ethers with acyl halides

Abstract

A variety of cyclic and acyclic ethers are efficiently reacted with acyl chlorides or acyl bromides to afford the ether-cleaved compounds of ω-chloro-or ω-bromoesters under high pressure conditions. The reactivity of ethers is found to be roughly depend on the basicity of the ether oxygen atom.     

Multicomponent Strecker Reaction under High Pressure

For the first time, uncatalyzed, high‐pressure (0.6 GPa) reactions with ketones have proven to be a powerful way to perform the three‐component Strecker synthesis of α‐amino nitriles in high yields. Two types of double Strecker reactions were achieved, but attempts to perform triple Strecker reactions were unsuccessful.     

Synthesis of Glycocinnasperimicin D

The first total synthesis of amino sugar antibiotic glycocinnasperimicin D ( 1 ) has been achieved by a convergent, three‐component coupling strategy. The key steps involve the Heck–Mizoroki reaction by using the iodophenyl glycoside 50 and acryl amide 32 to furnish the right core structure of 1 , and the construction of the urea glycoside employing the reaction of glycosyl isocyanate 8 with amino sugar 9 . Glycosyl isocyanate 8 was prepared by the oxidation of isonitrile 10 , which displayed excellent reactivity in the coupling event. Synthetic roadblocks, encountered during this synthetic effort, have led to the development of the α‐selective, Lewis acid catalyzed phenyl glycosylation process with 2‐amino‐hexopyranose and a procedure for acetonide deprotection without affecting the silyl ethers.     

A new approach to the neoglycopeptides: synthesis of urea- and carbamate-tethered N-acetyl-D-glucosamine amino acid conjugates

A novel approach to the synthesis of Fmoc-protected neoglycopeptide building blocks is described. Oxidation of N-acetyl-D-glucosamine isonitrile afforded the corresponding highly reactive glycopyranosyl isocyanate, which reacted with amino acid derivatives to furnish the corresponding urea- and carbamate-tethered Fmoc-protected N-acetyl-D-glucosamine amino acid conjugates in good yields. [reaction: see text]