In vitamin D research, there have been three milestones from the perspective of pharmaceutical studies. The first was the early stages of vitamin D research and involved the discovery of vitamin D and its physiological significance as an anti-rickets factor. The second was the elucidation of the vitamin D activation pathway in the body and the discovery of biologically active metabolites. The third has been characterized by the discovery of the differentiation-inducing properties of active vitamin D. This indicated the diversity of the physiological actions of active vitamin D, which initially had been thought only to contribute to bone and calcium metabolism. Because these physiological actions were clinically useful, the third discovery revealed opportunities for the development of drugs appropriate to specific purposes by synthesizing derivatives to separate biological effects. Six active vitamin D derivatives (maxacalcitol, calcipotriol, tacalcitol, paricalcitol, doxercalciferol, and falecalcitriol) based on the findings during the third milestone are now commercially available and contributing to current clinical practice. This article discusses the various milestones outlining vitamin D and derivatives in terms of pharmaceutical studies and practical syntheses of the six derivatives developed during the third milestone.
Investigations of biological processes by using peptide, protein, or its derivative are undoubtedly valuable. In this field, chemical synthesis of native or modified peptides/proteins is indispensable. Fragment condensation strategy, such as thioester method or native chemical ligation, is widely used for chemical synthesis of large peptides and proteins. C-Terminal peptide/protein thioesters have been used as building blocks for the fragment condensation strategy. Therefore, development of methodologies for preparing C-terminal peptide/protein thioesters is one of the most attracting theme in recent peptide/protein chemistry field. In this review, the methodologies for preparing C-terminal peptide/protein thioesters utilizing chemistry, biochemistry, or gene engineering are summarized.
In an effort to create reusable, Pd-leach-free catalysts, many heterogeneous catalysts have been developed with Pd immobilized on supports such as activated carbon, inorganic solids and polymers. Yet few of these immobilized Pd catalysts for C-C bond formations can claim both high recyclability (>10 times) and low Pd-leaching (<1 ppm). We successfully developed a practical Pd material, SGPd (Sulfur-modified GaAs(001) supported Pd) and SAPd (Sulfur-modified Au supported Pd) whose Pd was immobilized on sulfur-modified GaAs(001) or Au, respectively. With the lowest Pd-releasing levels and high recyclability, this is one of the best Pd materials thus far developed. It became clear that actual active species is released Pd in the reaction mixture through detailed mechanistic experiments. Because it leaches extremely low levels of Pd into reaction mixtures, removal of the residual Pd is unnecessary especially using SAPd, even in syntheses involving pharmaceutical ingredients.
A molecular machine has been defined as a discrete number of molecular components that perform mechanical-like movements in response to specific stimuli. In this account, we describe synthesis and dynamics of novel organosilicon compounds working as molecular machines. The introduction of the clutch-declutch mechanism into a molecular gear system was achieved using interconversion between silane and silicate. Molecular gyroscopes having a phenylene rotator encased in three long siloxaalkane spokes were synthesized; the merits of siloxaalkane chains, which are easily constructed and chemically stable and exhibit good crystallinity, are exerted in the synthesis. The silicon-based directed synthesis of rotaxanes without polar functional groups is described.
Bioactive natural products have been used as natural medicines from the beginning of human history. For the last several decades, their utility value has expanded from clinical medicine to basic science, and a number of natural products have been utilized as “bioprobes” for dissecting protein functions and cellular signaling pathways. However, the structural complexity and diversity of these compounds often hamper the necessary mode-of-action analysis and target identification, thereby limiting their utility in chemical biology. Consequently, mode-of-action analysis and target identification of complex natural products still remain a significant challenge in chemical biology and modern drug discovery. Herein, I highlight several examples of our efforts in this area. In the first half of this account, two examples of detailed mode-of-action analysis of complex bioactive natural products are presented. In the second half, a method for immobilizing natural products on solid surfaces is highlighted, and our recent efforts at detecting protein-ligand interactions utilizing this immobilization chemistry are summarized.
In(OTf)3-catalyzed cyclization of nitrogen- and oxygen-tethered acetylenic malonic esters provided various five to seven-membered heterocycles in moderate to excellent yield, and the reaction proceeded with no racemization and complete E-selectivity in the case of chiral and nonterminal alkynes. The synthetic utility was demonstrated by the total synthesis of (−)-salinosporamide A, a highly potent 20S proteasome inhibitor, and (+)-neooxazolomycin, a member of the oxazolomycin family of antibiotics.
Fluorinated compounds have drawn the attention of medicinal chemists because of their potential metabolic tolerance and modulation of drug efficacy. Thus stereo- and enantioselective construction of fluorinated carbon center is an important issue. In spite of remarkable progress in the last decade, the first effective method of catalytic enantioselective fluorination by nucleophilic fluorine reagent has been reported in this year. In this article, construction of fluorinated chiral center is reviewed being categolized into three classes.
Although oxidation of an alkyl C-H bond is an attractive method in organic synthesis, selectivities have been considered as a problematic issue of this reaction. Herein, selective oxidations of secondary or tertiary C-H bond using iron complexes are briefly reviewed.