Kinetic Resolution in Asymmetric Epoxidation using Iminium Salt Catalysis

The first reported examples of kinetic resolution in epoxidation reactions using iminium salt catalysis are described, providing up to 99% ee in the epoxidation of racemic cis-chromenes

Formal synthesis of (+)-lactacystin from l-serine

A formal, stereocontrolled synthesis of lactacystin has been completed from t-Bu-O-l-serine, providing the key intermediate 13, also useful for the generation of a range of C-9 analogues

Chlorine isotope composition in chlorofluorocarbons CFC-11, CFC-12 and CFC-113 in firn, stratospheric and tropospheric air

The stratospheric degradation of chlorofluorocarbons (CFCs) releases chlorine, which is a major contributor to the destruction of stratospheric ozone (O3). A recent study reported strong chlorine isotope fractionation during the breakdown of the most abundant CFC (CFC-12, CCl2F2, Laube et al., 2010a), similar to effects seen in nitrous oxide (N2O). Using air archives to obtain a long-term record of chlorine isotope ratios in CFCs could help to identify and quantify their sources and sinks. We analyse the three most abundant CFCs and show that CFC-11 (CCl3F) and CFC-113 (CClF2CCl2F) exhibit significant stratospheric chlorine isotope fractionation, in common with CFC-12. The apparent isotope fractionation (εapp) for mid- and high-latitude stratospheric samples are (-2.4±0.5) ‰ and (-2.3±0.4) ‰ for CFC-11, (-12.2±1.6) ‰ and (-6.8±0.8) ‰ for CFC-12 and (-3.5±1.5) ‰ and (-3.3±1.2) ‰ for CFC-113, respectively. Assuming a constant isotope composition of emissions, we calculate the expected trends in the tropospheric isotope signature of these gases based on their stratospheric 37Cl enrichment and stratosphere-troposphere exchange. We compare these projections to the long-term δ(37Cl) trends of all three CFCs, measured on background tropospheric samples from the Cape Grim air archive (Tasmania, 1978 – 2010) and tropospheric firn air samples from Greenland (NEEM site) and Antarctica (Fletcher Promontory site). From 1970 to the present-day, projected trends agree with tropospheric measurements, suggesting that within analytical uncertainties a constant average emission isotope delta is a compatible scenario. The measurement uncertainty is too high to determine whether the average emission isotope delta has been affected by changes in CFC manufacturing processes, or not. Our study increases the suite of trace gases amenable to direct isotope ratio measurements in small air volumes (approximately 200 ml), using a single-detector gas chromatography-mass spectrometry system

Conceptual Problems in Twentieth-Century Maine Maritime History

The article discusses the areas of research in twentieth-century Maine maritime history and available source material for that research

Abel Parker Upshur and The Dignity of Discipline

The political process of the American people has, through its custom of rewarding party constancy I placed individuals of widely varying aptitudes, abilities and interest in the office of the Secretary of the Navy. Despite the gross ineptitude of some, the short tenure of office of others, and the uninformed minds of a few, the mantel of the secretaryship of the Navy has fallen on the shoulders of some whose initial maritime acumen was relatively slight but which broadened and deepened in the furnace of accepted responsibility and on the forge of harsh deman

Book Reviews

The Equality of States in International Law. By Edwin De Witt Dickinson. (Cambridge: Harvard University Press, ig o. Harvard Studies in Jurisprudence, Vol. III.) Pp. ix, 424

The Naval Profession: Challenge and Response 1870-1890 and 1950-1970

History is important because it gives us a perspective from which to view our own concerns and problems which are frequently similar to those of other times. The naval profession faced similar problems in the two periods 1870-1890 and 1950-1970. In both periods the Navy had to develop a rational policy for the employment of the fleet as well as the means to make the fleet effective

Neutrality of British Dominions

The recent Cannes conference has revived the question of the -international status of the British dominions. Article IV of the proposed Anglo-French Alliance provided that the present treaty shall impose no obligation upon any of the dominions of the British Empire unless and until it is approved by the dominion concerned. In short, the dominions were left free to pursue an independent foreign policy in European affairs