A conventional new procedure for N-acylation of unprotected amino acids

The preparation of amide derivatives (4) by N-acylation of unprotected alpha-amino acids is easily achieved via readily available benzotriazolyl carboxylates (2a-d) or succinimidyl carboxylates (2e-f). These intermediates (2) are prepared from reaction of carboxylic acids (1) with 1-hydroxybenzotriazole (HO-Bt) or N-hydroxysuccinimide (HO-Su) in the presence of equimolar amounts of 1-ethyl-3-(3'-dimethylaminopropyl)carbodiimide hydrochloride (WSCI). The overall yields of the target compounds (4) were excellent, and this two-stage procedure could be applicable as an alternative procedure for one-pot reaction.     

Ferrocenylpyrazole—A versatile building block for hydrogen-bonded organometallic supramolecular assemblies

The crystal architectures of 5-ferrocenylpyrazole (1) and its metal complexes were investigated. Compound 1 can form non-solvated and chloroform-solvated crystals. In both cases, 1 forms a zigzag one-dimensional architecture via NH?N hydrogen bonds. The hydrogen bond exhibits a twofold disorder, which was shown to be static by solid-state ¹³C NMR. In the solvated crystal, the chloroform is released at 415 K, associated with melting of the crystal. The reaction of 1 with metal salts provided metal-centered ferrocenyl clusters [Zn(NO₃)₂(1)₄] (4), [Co(NO₃)₂(1)₄] (5), [CoCl₂(1)₄] (6), [Zn(NCS)₂(1)₂] (7), cis-[Pt(NH₃)₂(1)₂](PF₆)₂ (8), and trans-[Pt(NH₃)₂(1)₄](PF₆)₂ (9). In all of these complexes, 1 acts as a monodentate ligand. In 4, 5, and 7, the multinuclear units are joined via hydrogen bonds to form supramolecular chains. Two polymorphs were found for the crystals of 4. Both are composed of the same hydrogen-bonded chains, but their arrangements are different. 5-Ferrocenyl-1-tritylpyrazole (2) and 4-ferrocenyl-1-methylpyrazole (3) were also crystallographically characterized.     

Porcine dentin sialoprotein glycosylation and glycosaminoglycan attachments

Background  

Dentin sialophosphoprotein (Dspp) is a multidomain, secreted protein that is critical for the formation of tooth dentin. Mutations in DSPP cause inherited dentin defects categorized as dentin dysplasia type II and dentinogenesis imperfecta type II and type III. Dentin sialoprotein (Dsp), the N-terminal domain of dentin sialophosphoprotein (Dspp), is a highly glycosylated proteoglycan, but little is known about the number, character, and attachment sites of its carbohydrate moieties.     

An access to the β-anomer of 4'-thio-C-ribonucleosides: hydroboration of 1-C-aryl- or 1-C-heteroaryl-4-thiofuranoid glycals and its regiochemical outcome

We have developed a novel method for the synthesis of the β-anomer of 4'-thio-C-ribonucleosides from 3,5-O-(di-tert-butylsilylene)-4-thiofuranoid glycal. Palladium-catalyzed coupling of 1-tributylstannyl-4-thiofuranoid glycal with iodobenzene or a heteroaryl halide gave 1-C-phenyl- or 1-C-heteroaryl-glycals. Hydroboration of these glycals proceeded at the α-face, and subsequent alkaline hydrogen peroxide treatment of the resulting 2'-α-borane furnished the respective β-anomer of 4'-thio-C-ribonucleosides. These results demonstrate that this synthetic method has a wider scope in terms of heterocyclic base structure. During this study, unexpected Markovnikov-oriented hydroboration has been observed to lead to the respective 1'-α-boranes. These 1'-boranes were converted into either the ring-opened structure or the 2'-deoxy derivatives depending upon their stability.     

Correction to: Selective Cadmium Fluorescence Probe Based on Bis-Heterocyclic Molecule and its Imaging in Cells

Journal of Fluorescence - The original version of this article unfortunately contained a mistake. The equation under “Experimental -- Spectroscopic Studies” section should be corrected...     

Conformational Analysis and Selection of Odor‐Active Conformers: Synthesis of Molecules Designed for the Lily‐of‐the‐Valley(Muguet)‐Type Odor

The selection of odor‐active conformers and the construction of a model for a targeted odor type, i.e., for the lily‐of‐the‐valley odor, were examined. The disagreement of the odors of 1,3,4,5‐tetrahydro‐2‐benzoxepin derivative 1 and 3‐[4‐(tert‐butyl)phenyl]‐2‐methylpropanal ( 2 ) is discussed in terms of their stable conformers. The conformer active for the lily‐of‐the‐valley odor was investigated by conformational analyses of several related compounds. Based on the integrated model consisting of the assumed active conformers (Fig. 5), compounds anticipated to possess the lily‐of‐the‐valley odor were designed and synthesized. The odor of synthetic 7‐(tert‐butyl)‐1,2,4,5‐tetrahydro‐3H‐benzocyclohepten‐3‐one ( 8 ) and 3‐[4‐(tert‐butyl)phenyl]cyclopentanone ( 13 ) were evaluated by perfumers to have a floral odor and to recall the lily‐of‐the‐valley and lilac odors, respectively. Our methodology to design new odoriferous compounds, based on conformational analysis, selection of odor‐active conformers, and construction of a model, proved to be satisfactory.