Studies of Alicyclic α-Amino Acids. IV. Conformational Analysis of Alicyclic α-Amino Acids and Stereochemistry of the Strecker and the Bucherer Reactions
Studies of Alicyclic α-Amino Acids. IV. Conformational Analysis of Alicyclic α-Amino Acids and Stereochemistry of the Strecker and the Bucherer Reactions
作者:YOSHIFUMI MAKI、TAKASHI MASUGI、KOJI OZEKI
DOI:10.1248/cpb.21.2466
日期:——
Conformational analysis of a pair of isomeric alicyclic α-amino acids was made by comparison of relative rates for alkaline hydrolysis of their ethyl esters. It was found that in a sharp contrast with the case of 2-norbornanone, employment of the Strecker and the Bucherer reactions in 2-bornanone resulted in the predominant formation of the corresponding amino acid possessing exo-amino and endo-carboxyl groups. On the basis of this finding, the stereochemical courses of the Strecker and the Bucherer reactions in the synthesis of alicyclic α-amino acid are also discussed.
Magma evolution in the Purico ignimbrite complex, northern Chile: evidence for zoning of a dacitic magma by injection of rhyolitic melts following mafic recharge
作者:A. Schmitt、S. de Silva、R. Trumbull、R. Emmermann
DOI:10.1007/s004100000214
日期:2001.3
The 1.3 Ma Purico complex is part of an extensive Neogene-Pleistocene ignimbrite province in the central Andes. Like most other silicic complexes in the province, Purico is dominated by monotonous intermediate ash-flow sheets and has volumetrically minor lava domes. The Purico ignimbrites (total volume 80-100 km(3)) are divided into a Lower Purico Ignimbrite (LPI) with two extensive flow units, LPI I and LPI II; and a smaller Upper Purico Ignimbrite (UPI) unit. Crystal-rich dacite is the dominant lithology in all the Purico ignimbrites and in the lava domes. It is essentially the only lithology present in the first LPI flow unit (LPI I) and in the Upper Purico Ignimbrite, but the LPI II flow unit is unusual for its compositional diversity. It constitutes a stratigraphic sequence with a basal fall-out deposit containing rhyolitic pumice (68-74 wt% SiO2) overlain by ignimbrite with dominant crystal-rich dacitic pumice (64-66 wt% SiO2). Rare andesitic and banded pumice (60-61 wt% SiO2) are also present in the uppermost part of the flow unit. The different compositional groups of pumice in LPI II flow unit (rhyolite, andesite, dacite) have initial Nd and Sr isotopic compositions that are indistinguishable from each other and from the dominant dacitic pumice (epsilon Nd = -6.7 to -7.2 and Sr-87/Sr-86 = 0.7085-0.7090). However, two lines of evidence show that the andesite, dacite and rhyolite pumices do not represent a simple fractionation series. First, melt inclusions trapped in sequential growth zones of zoned plagioclase grains in the rhyolite record fractionation trends in the melt that diverge from those shown by dacite samples. Second, mineral equilibrium geothermometry reveals that dacites from all ignimbrite flow units and from the domes had relatively uniform and moderate pre-eruptive temperatures (780-800 degreesC), whereas the rhyalites and andesites yield consistently higher temperatures (850-950 degreesC). Hornblende geobarometry and pressure constraints from H2O and CO2 contents in melt inclusions indicate upper crustal (4-8 km) magma storage conditions. The petrologic evidence from the LPI II system thus indicates an anomalously zoned magma chamber with a rhyolitic cap that was hotter than, and chemically unrelated to, the underlying dacite. We suggest that the hotter rhyolite and andesite magmas are both related to an episode of replenishment in the dacitic Purico magma chamber. Rapid and effective crystal fractionation of the fresh andesite produced a hot rhyolitic melt whose low density and viscosity permitted ascent through the chamber without significant thermal and chemical equilibration with the resident dacite. Isotopic and compositional variations in the Purico system are typical of those seen throughout the Neogene ignimbrite complexes of the Central Andes. These characteristics were generated at moderate crustal depths (< 30 km) by crustal melting, mixing and homogenization involving mantle-derived basalts. For the Purico system, assimilation of at least 30% mantle-derived material is required.
Chiral bis(amino alcohol) silver complex derived from (+)-camphor
A chiral silver(I) complex was synthesized from the reaction of a chiralaminoalcoholderivedfrom (+)-camphor and silver nitrate, with the structure unambiguously disclosed by X-ray analysis and 2-D-NMR experiments. In this complex, the aminoalcohol molecule is a monodentate ligand through the amino nitrogen, requiring two aminoalcohol units which are coordinated to the silver and located orthogonally
手性银 (I) 配合物由衍生自 (+)-樟脑的手性氨基醇与硝酸银反应合成,其结构通过 X 射线分析和 2-D-NMR 实验明确公开。在该复合物中,氨基醇分子是通过氨基氮的单齿配体,需要两个氨基醇单元,它们与银配位并通过 NH-Ag-NH 轴正交定位。