Fast Deprotection of Synthetic Oligodeoxyribonucleotides Using Standard Reagents under Microwave Irradiation

Fast methods for the removal of permanent amide exo-cyclic protective groups widely used in phosphoramidite- method DNA synthesis are desirable for many genomics and proteomics applications. In this communication, we present a method for the deprotection of a range of N-acyl deoxyribonucleosides (T, dABz, dCBz, dCAc, dGibu, dGPAC) and synthetic oligodeoxyribonucleotides, ranging in length from 5-mer to 50-mer. Oligodeoxyribonucleotides were synthesized using standard amide protecting groups (dABz, dCBz, dGibu) and phosphoramidite chemistry on cis-diol solid phase support. This deprotection method utilizes 29% aqueous ammonia solution at 170\ub0C for 5 minutes under monomode microwave irradiation at a 20-nmole reaction scale. Reaction products were analyzed by TLC, RP-HPLC, CE, ESI-MS, real-time PCR, agarose gel electrophoresis, and by DNA uracil glycosylase (UDG) and phosphodiesterase I (PDE) enzymatic digestions.Peer reviewed: YesNRC publication: Ye

Rational and Predictable Chemoselective Synthesis of Oligoamines via Buchwald–Hartwig Amination of (Hetero)Aryl Chlorides Employing Mor-DalPhos

We report a diverse demonstration of synthetically useful chemoselectivity in the synthesis of di-, tri-, and tetraamines (62 examples) by use of Buchwald–Hartwig amination employing a single catalyst system ([Pd­(cinnamyl)­Cl]₂/<b>L1</b>; <b>L1</b> = <i>N</i>-(2-(di­(1-adamantyl)­phosphino)­phenyl)­morpholine, Mor-DalPhos). Competition reactions established the following relative preference of this catalyst system for amine coupling partners: linear primary alkylamines and imines > unhindered electron-rich primary anilines, primary hydrazones, <i>N</i>,<i>N</i>-dialkylhydrazines, and cyclic primary alkylamines > unhindered electron-deficient primary anilines, α-branched acyclic primary alkylamines, hindered electron-rich primary anilines ≫ cyclic and acyclic secondary dialkylamines, secondary alkyl/aryl and diarylamines, α,α-branched primary alkylamines, and primary amides. The new isomeric ligand <i>N</i>-(4-(di­(1-adamantyl)­phosphino)­phenyl)­morpholine (<i>p</i>-Mor-DalPhos, <b>L2</b>) was prepared in 63% yield and was crystallographically characterized; the [Pd­(cinnamyl)­Cl]₂/<b>L2</b> catalyst system exhibited divergent reactivity. Application of the reactivity trends established for [Pd­(cinnamyl)­Cl]₂/<b>L1</b> toward the chemoselective synthesis of di-, tri-, and tetraamines was achieved. Preferential arylation was observed at the primary alkylamine position within 2-(4-aminophenyl)­ethylamine with [Pd­(cinnamyl)­Cl]₂/<b>L1</b> and 4-chlorotoluene (affording <b>5a</b>); the alternative regioisomer (<b>5a′</b>) was obtained when using [Pd­(cinnamyl)­Cl]₂/<b>L2</b>. These observations are in keeping with coordination chemistry studies, whereby binding of 2-(4-aminophenyl)­ethylamine to the in situ generated [(<b>L1</b>)­Pd­(<i>p</i>-tolyl)]⁺ fragment occurred via the primary amine moiety, affording the crystallographically characterized adduct [(<b>L1</b>)­Pd­(<i>p</i>-tolyl)­(<i>N</i>H₂CH₂CH₂(4-C₆H₄NH₂)]⁺OTf^– (<b>7</b>) in 72% yield

Fracture in Equiaxed Two Phase Alloys: Part I. Fracture in Alloys with Isolated Elastic Particles

Fracture in equiaxed two phase alloys containing isolated elastic particles has been analyzed from the viewpoint of a recently proposed model for fracture initiation and propagation in such materials. This model predicts fracture toughness parameters in terms of the microstructural geometry, relative phase volume fractions, and tensile properties of the materials. Predictions of the model are tested experimentally for two phase Co-CoAl alloys over a wide range of compositions, and the results indicate good agreement between predicted and observed fracture toughnesses