This new understanding and demonstration of features printed by proximity x-ray lithography allows a revolutionary extension and simplification of otherwise established processes for microfabrication. The ability to produce fine features is controlled predominantly by diffraction and photoelectron blur. The diffraction manifests itself as feature 'bias'. In the classical approach the bias is minimized. Bias optimization in terms of mask/wafer gap and resist processing allows the formation, on a wafer, of features smaller than those on the mask: thus producing local 'demagnification'. This demagnification (×3 − ×6) is achieved without lenses or mirrors, but it offers the same advantages as projection optical lithography in terms of critical dimension control. The photoelectron blur is more or less pronounced depending on exposure dose and development conditions. Resist exposure and process can be optimized to utilize a ∼50% photoelectron energy loss range. In consequence proximity x-ray lithography is extensible to feature sizes below 25 nm, taking advantage of comparatively large mask features (>100 nm) and large gaps (30-15 µm). The method is demonstrated for demagnification values down to ×3.5. To produce DRAM half-pitch fine features, techniques such as multiple exposures with a single development step are proposed.

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Herein we report a general method of the asymmetric synthesis of 1,4‐substituted 1,2,3‐triazole containing amino acids via copper(I) iodide catalyzed “click reaction” between azides and chiral Ni(II) complexes of Schiff bases of (S)‐ or (R)‐BPB with alkyne side chain derivatised amino acids. The final Ni(II) complexes were decomposed with aqueous HCl and the 1,4‐substituted 1,2,3‐triazole containing amino acids isolated with excellent enantioselectivities (>99% ee). The chiral auxiliary ligand (BPB=N‐benzyl proline benzophenone) can be recycled and reused for the synthesis of starting Ni(II) complexes.

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The acetalization of phenyl 1-thio-α-L-arabinopyranoside with 2,3-butanedione in the medium of MeOH-CH(OMe) 3 -CSA proceeded with the prevailing formation of the corresponding 3,4-bisacetal that further was converted in compounds, which were regio-and stereoisomers of disaccharide block of OSW-1. O HO O SPh HO OH HO O SPh HO OAc I II IIIIn the sugar chemistry the necessity to work with awkward polyol systems makes the protective groups extremely important [1]. In the course of the planned synthesis of disaccharide block I for anticancer steroid OSW-1 based on the known components, glycosidedonor II and acceptor III [2, 3] (Scheme 1) we tested 2,3-butanedione in conditions described in [4] for the selective protection of the 3,4-diol moiety of triol II in the form of butane 2,3-bisacetal. The butane 2,3-bisacetal and the other similar protective groups introduced into the synthetic practice by Liu group [5] are known to provide a selective blocking in cycles of trans-vicinal diols, impart the products a crystalline structure, desired conformational rigidity, etc. [6].As seen from the structure of triol II all its hydroxy groups are located in the trans-equatorial reciprocal position, and here the possibility of the regiocontrolled acetalization depends mainly on the steric factors. In the experimental test of triol II acetalization by heating with excess 2,3-butanedione in the medium of MeOH-CH(OMe) 3 -camphorsulfonic acid (CSA) (catalyst) we obtained two expected acetals IV and V in the ratio ~3 : 1 and in the overall yield 80%. The main bisacetal IV is a crystalline substance easily isolated from compound V by chromatography on SiO 2 . Minor bisacetal V is oily substance containing ~10% of unidentifi ed isomeric compound. The assignment of the structure of regioisomeric acetals IV and V was carried out applying spectral data. Their 1 H NMR spectra contain a characteristic signal C 1 H which in the spectrum of 2,3-acetal V is located downfi eld (doublet, δ 4.77 ppm, J 9.6 Hz) with respect to the corresponding signal in the spectrum of compound IV (δ 4.47 ppm, d, J 9.35 Hz) because of the electron-withdrawing inductive effect of the closely Scheme 1.