Tridensenal,A Sesquiterpene of Novel Skeleton from the Taiwanese Liverwort Bazzania Tridens

The sesquiterpene aldehyde, tridensenal, of previously unknown skeleton was isolated from the Taiwanese liverwort Bazzania tridens. The structure of tridensenal was elucidated on the basis of spectral data and proved by synthesis of the diastereomeric mixture.     

Impact of Higher‐Order Structuralization on the Adsorptive Properties of Metal–Organic Frameworks

The structural processing of metal–organic frameworks (MOFs) over multiple length scales is critical for their successful use as adsorbents in a variety of emerging applications. Although significant advances in molecular‐scale design have provided strategies to boost the adsorptive capacities of MOFs, relatively little attention has been directed toward understanding the influence of higher‐order structuralization on the material performance. Herein, we present the main strategies that are currently available for the structural processing of MOFs and discuss the influence these processes can impart on the adsorptive properties of the materials. In all, this intriguing area of research is expected to provide significant opportunities to enhance the properties of MOFs further, which will ultimately aid in their optimization in the context of specific real‐world applications.     

NUMBER CONCENTRATION, SIZE DISTRIBUTION AND FINE PARTICLE FRACTION OF TROPOSPHERIC AND STRATOSPHERIC AEROSOLS

1. Introduction The number concentration and size distribution of at-mospheric particles are the two major parameters for aerosol radiative forcing calculation, as the aerosol bur-dens affect the radiative transfer of solar and terrestrial emissions, while the size distribution of atmospheric aerosol is critical to all climatic influences (IPCC, 2001). However most measurements on the characteristics of the number-size distribution were carried out near the earth surface, with only a few exte…     

Annulenediones having quinonoid properties

Chemical and Electrochemical reductions of bisdehydro[14]- and [18]annu1ened1ones clearly revealed their quinonoid nature.     

Studies in organic mass spectrometry—V: N-arylsulphonyliminopyridinium betaines

The mass spectral fragmentation of N-arylsulphonyliminopyridinium betaines has been rationalized using high resolution mass spectrometry as well as deuterium labelling. The most characteristic features are a very facile N S bond cleavage and skeletal rearrangements accompanied by the expulsion of SO₂ from the molecular ion and the [M 1] ion to the corresponding ionized N-aryliminopyridinium betaines and azacarbazoles, respectively. The presence of methyl substituents at the α-position of the pyridine ring has a significant effect on the mode of the fragmentation.     

Allostery of the two-state model of hemoglobin studied by ECEPP energy minimization

Recently, a powerful parallel-vector processor became available for molecular science. A new FORTRUN program was coded to treat the whole hemoglobin molecule with twofold symmetry. Using the X-ray coordinates of deoxyhemoglobin and oxyhemoglobin, minimum energy conformations were obtained for both the T-state and the R-state on the two-state model of allostery. From them, further energy minimization was performed with simple perturbation to bring the proximal region close to the heme group instead of oxygen binding, and the structural changes and energy changes were investigated. The difference of calculated energy changes between T and R was semiquantitatively in agreement with the experimental value 2.7 kcal/mol for one oxygen binding. When the perturbation was exerted on the alpha-subunits, the energy change within the perturbed alpha-subunits in the T-state gave a main contribution, and in the R-state, the structural changes of the alpha-subunits were specifically large. When the perturbation was exerted on the beta-subunits, the intersubunit interaction energy between alpha1 and beta2 (alpha2 and beta1) was dominant in the difference of the energy changes between T and R.     

Tributylstannyl radical-catalyzed reaction of 1,2,3-selenadiazoles with olefins or dienes

It was found that the reaction of 1,2,3-selenadiazoles derived from cyclic ketones with olefins or dienes was markedly promoted by a catalytic amount of tributylstannyl radical, which was generated in situ from tributylstannyl hydride or allyltributylstannane and AIBN, to give the corresponding dihydroselenophenes in moderate to good yields. In contrast, when 1,2,3-selenadiazoles prepared from linear and aromatic ketones were used as substrates, the same reaction did not take place, and alkynes were formed as the sole product.