Subnanometer-accuracy z-position monitor mask for optical lithography

A lithographic test pattern, the phase shift grating (PSG) z monitor, is introduced. Through the use of phase shift techniques, position errors of images in the z-direction translate into lateral shifts in the printed pattern. The lateral shifts are easily measurable using an overlay metrology tool. Each z monitor pattern in a test mask can be directly read for the sign and magnitude of the z error. When the experimental conditions, namely, the period of a PSG and a coherent factor of the lithography tool simultaneously satisfies a criterion of the asymmetric two-beam interference between the zeroth-order ray and either of the two first-order rays of diffraction, the linearity of a z-vs-overlay curve is always complete and the slope of the curve is constant everywhere in the image field. Using state-of-the-art overlay metrology tools, we realized subnanometer-order accuracy in the z measurement.     

Dynamic recording of a digital hologram with single exposure by a wave-splitting phase-shifting method

The wave-splitting phase-shifting digital holography using a pixelated microretarder array is proposed. By using four intensity images recorded by the pixelated microretarder array, Stokes parameters of the incident wave can be calculated. The fully complex amplitude distribution of the object wave can be obtained by using Stokes parameters, if the polarization states of the object and reference waves are linear and orthogonal. Two sets of experimental results are provided to verify the feasibility of the proposed method. One is the result for a movie recording using a CW laser and the other is the result for instant recording using a single pulsed laser.     

Sequence Dependence of Fluorescent Quenching of Chromophores Covalently Bonded to Oligo-DNAs before and after Duplex Formation

The labeling of oligo- and polynucleotides with fluorescent probes is an important technique for the analysis of DNAs and RNAs. The effect of duplex formation with complementary oligo-DNA on the quenching behavior of two fluorescent chromophores (eosin, Eo and tetramethylrhodamine, TMR) attached to the 5′-terminal of various 10mer oligo-DNAs was investigated and the dependence of the quenching on DNA base sequence is discussed. We found that guanine residues played a major role in the quenching of the fluorescence of the chromophores. Guanine residues on the complementary DNA near the chromophores, in particular, had a significant influence on the quenching.     

Simultaneous determination of testosterone, cortisol, and dehydroepiandrosterone in saliva by stable isotope dilution on-line in-tube solid-phase microextraction coupled with liquid chromatography–tandem mass spectrometry

We have developed a simple and sensitive method for the simultaneous determination of testosterone (TES), cortisol (CRT), and dehydroepiandrosterone (DHEA) in saliva by automated online in-tube solid-phase microextraction (SPME) coupled with liquid chromatography–tandem mass spectrometry (LC–MS/MS) using a Discovery HS F5 column. The optimum in-tube SPME conditions were 25 draw/eject cycles of 40 μL of sample at a flow rate of 200 μL/min using a Supel-Q PLOT capillary column as an extraction device. The extracted compounds were easily desorbed from the capillary by passage of the mobile phase, and no carryover was observed. The in-tube SPME LC–MS/MS method showed good linearity with correlation coefficients r?≥?0.9998 for TES, CRT, and DHEA using their respective stable isotope-labeled internal standards. The intra-day and inter-day precisions (relative standard deviations) were below 4.9 and 8.5 % (n?=?5), respectively. This method was successfully utilized to analyze TES, CRT, and DHEA in saliva samples without any other pretreatment or interference peaks, and the quantification limits (S/N?=?10) of TES, CRT and DHEA were about 0.01, 0.03 and 0.29 ng/mL saliva, respectively. The recoveries of these compounds spiked into saliva samples were each above 94 %. This method was applied to analyze changes in salivary TES, CRT, and DHEA levels resulting from stress and fatigue load.     

Practical Synthesis of (20S)‐10‐(3‐Aminopropyloxy)‐7‐ethylcamptothecin,a Water‐Soluble Analogue of Camptothecin

A robust, practical synthesis of (20S)‐10‐(3‐aminopropyloxy)‐7‐ethylcamptothecin (T‐2513, 5 ), which is a water‐soluble analogue of camptothecin, has been developed. The key step in this synthesis is a highly diastereoselective ethylation at the C20 position by using N‐arylsulfonyl‐(R)‐1,2,3,4‐tetrahydroisoquinoline‐3‐carboxylic acid ester as a chiral auxiliary, which affords the key intermediate ethyl‐(S)‐2‐acyloxy‐2‐(6‐cyano‐5‐oxo‐1,2,3,5‐tetrahydroindolizin‐7‐yl)butanoate ( 8 k ) in 93 % yield and 87 % de. Optically pure compound 8 k was obtained by a single recrystallization from acetone and its further elaboration through Friedlander condensation afforded compound 5 . This synthesis does not require any chromatographic purification steps and can provide compound 5 on a multi‐gram scale in 6.3 % overall yield (16 steps).     

Total synthesis of PDE-I and -II by copper-mediated double aryl amination

A concise total synthesis of PDE-I and -II featuring copper-mediated double aryl amination with the combination of CuI, CsOAc, and Cs₂CO₃ is described. The highly substituted pyrroloindole skeleton was constructed by a one-pot five-step sequence including double aryl amination, β-elimination, deprotection of a Cbz group, and unexpected formation of an indole via removal of an Ns group followed by rearomatization. The undesired elimination of the protecting group (Ns group) was hampered by using the Boc group as a protecting group in the second-generation synthesis, which excluded the reduction of the indole required in the first-generation synthesis.     

Oxygenation and chlorination of aromatic hydrocarbons with hydrochloric acid photosensitized by 9-mesityl-10-methylacridinium under visible light irradiation

Efficient photocatalytic oxygenation of toluene occurs under visible light irradiation of 9-mesityl-10-methylacridinium (Acr⁺–Mes) in oxygen-saturated acetonitrile containing toluene and aqueous hydrochloric acid with a xenon lamp for 15 h. The oxygenated products, benzoic acid (70 %) and benzaldehyde (30 %), were formed after the photoirradiation. The photocatalytic reaction is initiated by intramolecular photoinduced electron transfer from the mesitylene moiety to the singlet excited state of the Acr⁺ moiety of Acr⁺–Mes, which affords the electron-transfer state, Acr^?–Mes^?+. The Mes^?+ moiety can oxidize chloride ion (Cl^?) by electron transfer to produce chlorine radical (Cl^?), whereas the Acr^? moiety can reduce O₂ to O ₂ ^?? . The Cl^? radical produced abstracts a hydrogen from toluene to afford benzyl radical in competition with the bimolecular radical coupling of Cl^?. The benzyl radical reacts with O₂ rapidly to afford the peroxyl radical, leading to the oxygenated product, benzaldehyde. Benzaldehyde is readily further photooxygenated to yield benzoic acid with Acr^?–Mes^?+. In the case of an aromatic compound with electron-donating substituents, 1,3,5-trimethoxybenzene, photocatalytic chlorination occurred efficiently under the same photoirradiation conditions to yield a monochloro-substituted compound, 2,4,6-trimethoxychlorobenzene.     

Design and synthesis of 2-(1,3-dialkoxy-2-methylpropan-2-yl)-1,3-diarylpropanes as tethering units for folded H-stacking polymers

1,3-Diarylpropenes 9 having a 1,3-dialkoxy-2-methylpropan-2-yl group were designed as tethering monomers for folded H-stacking polymers, and were readily synthesized from 2-ethoxymethylidene malonate in four- or five-steps, including a facile sequential addition–elimination–addition reaction of benzyl zinc reagents. The preference for the closed (stacked) conformation in the resulting 2-substituted 1,3-diarylpropanes 9 was evaluated using MM2 calculations, ¹H NMR analyses, and fluorescence measurements. Copolymerization of the resulting monomers 9 with compounds containing π-units provided polymers with blue-shifted UV-absorptions both in solution and as films, compared with that of a model compound containing a single π-unit. This optical property is unique to H-aggregated π-units.