Total synthesis of (-)-laulimalide

(-)-Laulimalide (1), a structurally novel macrolide isolated in trace amounts from marine sponges, promotes abnormal tubulin polymerization and apoptosis in vitro, with a similar mode of action to that of Taxol(R), but with potentially less susceptibility to multidrug resistance. Herein, a flexible and convergent asymmetric synthesis of (-)-laulimalide is described. This synthesis featured a highly diastereoselective Sakurai reaction of 2 with 3 and a regioselective macrolactonization of an unprotected vicinal diol. Laulimalide was synthesized in 25 steps (longest linear; 36 overall) in 3.5% overall yield, providing a uniquely short and efficient route to 1 and its analogues.     

A New Method for the Syntiiesis of 1-Aryl Phthalazines

A simple versatile method for the conversion of 1 -aroyl-2-(substituted benzylidene)-hydrazines to 1-aryl-phthalazines using polyphosphate ester (PPE) is described.     

Generation of 250 mW narrowband pulsed ultraviolet light by frequency quadrupling of an amplified erbium-doped fiber laser

We demonstrate a high-power, narrowband pulsed source at 390 nm by two stages of frequency doubling in periodically poled MgO:LiNbO(3) and periodically poled KTiOPO(4) of an amplified, passively mode-locked fiber laser. With a frequency quadrupling efficiency of 5.5% and a 0.1 nm bandwidth, the 250 mW ultraviolet source is a suitable compact pump source for many entanglement-based quantum information processing tasks.     

Electrodeposition and characterization Zn-Co alloy

The present work details optimization of a stable acid chloride bath for electroplating of bright Zn-Co alloy on mild steel using gelatin and glycine as additives. It was found that the addition of gelatin along with glycine changed the deposition pattern markedly. A suitable bath has been formulated using conventional Hull cell experiments. The bath under plating conditions were found to exhibit anomalous codeposition with preferential deposition of less noble (zinc) over more noble (cobalt) as characterized by Zn-Fe group metal alloys. Investigation revealed that the current density (c.d.), temperature, and pH of the bath have strong effect on the composition of the deposit. Influence of bath constituents and operating parameters on appearance and composition of deposits were studied as measure of their performance against corrosion. A variety of deposits were obtained and their corrosion resistances were measured by Tafel method with/without chrome passivation. Experimental results demonstrated the fact that the corrosion resistances of Zn-Co alloys increased with percent of Co in the deposit except at very high c.d. This is due to the fact at very high c.d. the deposit becomes very porous and thick as evidenced by SEM image. The formation of Zn-Co alloy is confirmed by EDAX analysis. A stable chloride bath for Zn-Co alloy deposition has been proposed and discussed. The formation of passive film on chromatization is indicated by almost same E _corr value of all Zn-Co electroplates irrespective of the current densities at which they have been deposited. Published in Russian in Elektrokhimiya, 2009, Vol. 45, No. 7, pp. 811–816. The text is published in the original.     

Generation and propagation of a picosecond acoustic pulse at a buried interface: time-resolved x-ray diffraction measurements

We report on the propagation of coherent acoustic wave packets in (001) surface oriented Al0.3Ga0.7As/GaAs heterostructure, generated through localized femtosecond photoexcitation of the GaAs. Transient structural changes in both the substrate and film are measured with picosecond time-resolved x-ray diffraction. The data indicate an elastic response consisting of unipolar compression pulses of a few hundred picosecond duration traveling along [001] and [001] directions that are produced by predominately impulsive stress. The transmission and reflection of the strain pulses are in agreement with an acoustic mismatch model of the heterostructure and free-space interfaces.