Diphenylprolinol silyl ether was found to be an effective organocatalyst for promoting the asymmetric, catalytic, intramolecular [6 + 2] cycloaddition reactions of fulvenes substituted at the exocyclic 6-position with a δ-formylalkyl group to afford synthetically useful linear triquinane derivatives in good yields and excellent enantioselectivities. The cis-fused triquinane derivatives were obtained exclusively; the trans-fused isomers were not detected among the reaction products. The intramolecular [6 + 2] cycloaddition occurs between the fulvene functionality (6π) and the enamine double bond (2π) generated from the formyl group in the substrates and the diphenylprolinol silyl ether. The absolute configuration of the reaction products was determined by vibrational circular dichroism. The reaction mechanism was investigated using molecular orbital calculations, B3LYP and MP2 geometry optimizations, and subsequent single-point energy evaluations on model reaction sequences. These calculations revealed the following: (i) The intermolecular [6 + 2] cycloaddition of a fulvene and an enamine double bond proceeds in a stepwise mechanism via a zwitterionic intermediate. (ii) On the other hand, the intramolecular [6 + 2] cycloaddition leading to the cis-fused triquinane skeleton proceeds in a concerted mechanism via a highly asynchronous transition state. (iii) The fulvene functionality and the enamine double bond adopt the gauche-syn conformation during the C-C bond formation processes in the [6 + 2] cycloaddition. (iv) The energy profiles calculated for the intramolecular reaction explain the observed exclusive formation of the cis-fused triquinane derivatives in the [6 + 2] cycloaddition reactions. The reasons for the enantioselectivity seen in these [6 + 2] cycloaddition reactions are also discussed.

A dream come true: ABT‐341 was synthesized in high yield with excellent diastereo‐ and enantioselectivity in a one‐pot process mediated by a diphenylprolinol silyl ether (see scheme; TMS=trimethylsilyl). Thus, an asymmetric Michael reaction, a domino Michael/Horner–Wadsworth–Emmons reaction combined with a retro‐aldol reaction, base‐catalyzed isomerization, amide‐bond formation, and reduction of the nitro group all took place in a single flask.

Ein Traum wird wahr: ABT‐341 wurde in hohen Ausbeuten und mit exzellenter Diastereo‐ und Enantioselektivität in einem durch einen Diphenylprolinolsilylether vermittelten Eintopfprozess synthetisiert (siehe Schema; TMS=Trimethylsilyl). Somit fanden eine asymmetrische Michael‐Reaktion, eine Michael‐/Horner‐Wadsworth‐Emmons‐Dominoreaktion, eine Retroaldolreaktion, eine basenkatalysierte Isomerisierung, die Bildung einer Amidbindung und die Reduktion der Nitrogruppe in einem einzigen Reaktionskolben statt.

Acquired immunodeficiency syndrome (AIDS) is caused by infection with the human immunodeficiency virus (HIV). Although treatments against HIV infection are available, AIDS remains a serious disease that causes many deaths annually. Although a variety of anti‐HIV drugs have been synthesized and marketed to treat HIV‐infected patients, nucleoside analogue reverse transcriptase inhibitors (NRTIs), which mimic nucleosides, are used extensively and remain a subject of interest to medicinal chemists. However, HIV has acquired drug resistance against NRTIs, and thus the struggle to find novel therapies continues. In this review, we trace the trajectory of NRTIs, focusing on the synthesis, mechanisms of action and applications of NRTIs that have been developed.

To characterize easily the state of real metal surfaces in ambient environments, we have developed an extremely sensitive technique for surface analysis using photoelectron emission phenomena as a function of temperature. We will call this method temperature-programmed photoelectron emission (TPPE). The emitted electrons are detected by a gas-flow Geiger counter with Q gas. The TPPE measurement is performed by scanning the wavelength of incident UV light at different temperatures in the temperature-increase and subsequent temperature-decrease process between 25 and 350°C. A photoelectron emission (PE) spectrum representing the curve of PE intensity vs wavelength is obtained at each temperature. The number of emitted electrons in a PE spectrum is termed PE total count. The PE total count as a function of the measurement temperature was investigated for 17 kinds of commercial rolled metal sheets. The metals were distinctly classified into two main groups A and B, the former indicating a temperature-dependent PE total count and the latter a virtually temperature-independent PE total count. Group A included Al, Pt, Pb, Cu, Ag, Au and Ni; group B included Ta, Ti, Mo, Pd, W, Fe, Co, Zn, Nb and Sn. With group A, the greater amount of adsorbed oxygen present at the initial surface was found by XPS to change to the oxide oxygen after TPPE measurement. This chemical change is suggested to play a substantial role in the temperature dependence of the PE total count.