Recent advances in the methodology for the synthesis of vitamin D analogs are reviewed. The synthetic methods of vitamin D are classified into three types of the approaches ; (1) conversions from steroid compounds (2) convergent synthesis (3) partial conversions from readily available vitamin D2 or D3. Their merits and demerits are discussed by using some examples from recent literatures (mainly after 1985). Modifications of vitamin D by fluorine atom (s) are also discussed briefly.
A 1, 3-polyhydroxylated chain is often found on the backbone of biologically important antibiotics. The acyclic nature of 1, 3-polyol and a regular array of many hydroxy groups are main obstacles to synthetic studies and, therefore, many synthetic efforts have been made to this end. This article reviews recent progress in the synthesis of 1, 3-polyols and its application.
Cyclopolymerization, which does not need a cyclic derivative as monomer, is a direct method for producing rings and polymer chain at the same time. Monomers forming 5-7 membered-rings have been generally studied. We established the synthesis of polymers with macrocyclic units via cyclopolymerization of bifunctional monomers containing oxyethylene units. Poly (crown ether) s and poly (cryptande) s are synthesized through the polymerizations of divinyl ethers and diepoxides, poly (thia-crown ether) s through diepisulfides, and poly (crown lactone) s through the monomers having acrylic and allylic groups. These polymers except for poly (crown lactone) s consist essentially of cyclic constitutional repeating units, and have the cation-binding properties. Cyclopolymerization of divinyl ethers is a facile method for producing optically active poly (crown ether) s which exhibit chiral recognition towards α-amino acids. For the cyclopolymerization of divinyl ether derived from chiral 3, 3'-disubstituted- 1, 1'-bi-2-naphthol, the asymmetric induction in the polymer main chain was concluded by the analysis of 1H NMR spectra of polymers.
A photographic process includes a sensitive chemical amplification step catalyzed by silver metal (Ag°) nuclei which are responsible for the formation of silver images. Although the Ag nuclei are normally produced by exposure to light, we observed that they are formed by treatment of an unexposed negative film with a certain kind of compound (a nucleating reagent) without exposure. Moreover, a linear relationship clearly existed between the optical density of the film developed and the logarithm of concentration of the compound over the range from 2.0 × 10-8 M to 8.0 × 10-8 M. On the basis of the findings, a highly sensitive photographic assay procedure of α-amylase by using the photographic development process was proposed. In line with the concept, an a-amylase substrate incorporating the nucleating reagent newly observed, as a labeling component, was synthesized regioselectively. The analysis of enzymatic degradation proved that the substrate synthesized can release efficiently the nucleating reagent without loss of photographic activity. This provides the first successful approach for application of a photographic system into a quantitative determination of trace organic molecules.
In the reaction of tribromoborane with 1-alkynes, cis-addition occurred to give [Z] -2-bromo-1-alkenylboranes. On the other hand, bromoboration reaction of acetylene gave trans-addition product. Both reactions proceeded stereoselectively and (bromoalkenyl) boranes could be obtained with high selectivity. trans-Alkenes, α, β-unsaturated ketones, α, β-unsaturated esters were prepared stereoselectively by the stepwise crosscoupling reaction of the haloboration adducts. As the application, prostaglandin B1 methyl ester was synthesized. This method was also used for the synthesis of the polyenes which were converted to the polycyclic compounds by the intramolecular Diels-Alder reaction. Bromoboration reaction of allene provided (2-bromoallyl) borane and the reaction of (2-bromoallyl) borane with carbonyl compounds was also described.