Diversity‐oriented synthesis : The multicomponent reaction of α‐isocyano amides, aldehydes or ketones, and amines affords N‐(cyanomethyl)amides, presenting the fourth class of products from this combination of reagents (see scheme). The scope of the reaction is very broad and various functional groups are tolerated. The outcome of the reaction can also be directed to the formation of 2H‐2‐imidazolines by AgI catalysis.
Mild reaction conditions are the advantage of the title reaction, which allows straightforward entry to a variety of ynamides starting from readily available 1,1‐dibromo‐1‐alkenes, which act as attractive alkynylating agents (see scheme; EWG=electron‐withdrawing group, DMF=N,N‐dimethylformamide).
Searching for “intelligence” : Azurin–PNIPAM conjugates were prepared by site‐directed mutagenesis followed by protein reconstitution by using imidazole‐conjugated poly(N‐isopropylacrylamides). The polymer‐bound imidazole acts as a ligand in the active site of the blue copper protein azurin. The bioconjugates showed thermosensitive behavior in electron‐transfer processes with reduced cytochrome c.
Effect of a PAH on base pairing : A polycyclic aromatic hydrocarbon (PAH) covalently linked to the N6‐position of a dangling deoxyadenosine residue (see scheme) of an oligonucleotide increases target affinity, but decreases base‐pairing selectivity. Melting point increases of up to 28 °C (14 °C per residue) were observed, and 20 out of 24 mismatch‐containing duplexes are stabilized more strongly by the PAH substituent than their perfectly matched counterpart.
Under Lewis acid condition, N‐methyl‐3‐phenyl‐N‐(2‐(Z)‐phenylethenyl)‐cis‐oxiranecarboxamide undergoes elegant double cyclizations to give interesting products. 相似文献
On solid ground : A new solid‐phase synthesis of N‐linked glycans featuring 1) highly stereoselective β‐mannosylation and microfluidic α‐sialylation and 2) efficient glycosylation of the N‐phenyltrifluoroacetimidate units on JandaJel resin is reported. Reagent concentration effects by a fluorous solvent are effectively applied, and the use of these methods results in the first synthesis of a sialic acid containing complex‐type N‐glycan on a solid support.
Economical approach : The first organocatalytic asymmetric intramolecular hydroarylation of phenol‐ and aniline‐derived enals offers one of the most straightforward and atom‐economic approaches to enantioriched chromans and tetrahydroquinolines (up to 96 % ee; see scheme).
A convenient route with high stereo control to γ‐acetoxy dienoates is provided by the reaction of methyl propiolate with aldehydes in the presence of ZnEt2 and N‐methylimidazole at room temperature, followed by the catalytic conversion of the resulting γ‐hydroxy‐α,β‐acetylenic esters with p‐N,N‐dimethylaminopyridine (DMAP) in acetic anhydride (see scheme).
2009: A boraanthracene odyssey : General routes to boraanthracene derivatives—long proposed, but never observed—are disclosed, along with the structural and photophysical properties of these compounds and their remarkable reactivity towards oxygen.
Efficient route : A novel RhI‐catalyzed regio‐ and stereospecific carbonylation reaction of (1‐alkynyl)cyclopropyl ketones by selective activation of a carbon? carbon σ bond of the cyclopropane ring was demonstrated (see scheme). This method provides a general, efficient, stereoselective route to synthesise 1,3,5‐trisubstituted and 1,3,5,6‐tetrasubstituted 5,6‐dihydrocyclopenta[c]furan‐4‐one with convertible functional groups.
Original and ambivalent : We describe the preparation of a series of new potassium trifluoroborates 1 , and the study of their behaviour in a Pd0‐catalyzed cross‐coupling reaction. We found that compounds 1 are endowed with original properties as they behave as nucleophilic cross‐coupling partners chemoselectively, but also as ambivalent synthons. The usefulness of this methodology has been successfully illustrated by the first total synthesis of an N‐acyl spermidine.
One stereocenter makes all the difference : The synthesis and biological evaluation of 17‐epi‐cortistatin A is reported from a common intermediate used to procure natural cortistatin A. The synthesis features a unique stereocontrolled Raney‐Ni reduction process that can be employed to reliably produce both α‐ and β‐configured D‐ring aryl steroids. Biological evaluations of these “cortalogs” are reported for the first time.
All light and no heat? Structure–property relationships for photochromic and thermochromic N‐salicylideneanils have been revised (see picture). One derivative has a packed crystal structure, is photochromic and exhibits an infinitely slow thermal back relaxation of technological interest. Complexation of the anils to transition metals has also been studied.
Why bigger is better : A “steric wall” created by the N‐(2,6‐diisopropylphenyl) substituent on the bulky NHC ligand IPr (1,3‐bis(2,6‐diisopropylphenyl)imidazol‐2‐ylidene) guides the reactants to and from the Pd center through weak, fleeting (IPr)H–Pd interactions that help the oxidative addition intermediate escape “the anti‐trap”. The alternative “side” approach leads to transmetalation (the rate‐limiting step) for which a novel Pd–Zn interaction was identified.
Robust protocol! A diverse array of piperazine scaffolds was obtained by a robust solid‐phase‐synthesis protocol involving multistep elaboration of a resin‐bound aziridine (see scheme). Microwave‐assisted on‐resin protectinggroup introduction and manipulation as well as intramolecular Fukuyama–Mitsunobu cyclization conditions were key features.
Economical atoms : 2‐Cyclopenten‐1‐ones, 5‐alkylidenefuran‐2(5 H)‐ones and indan‐1‐ones have been synthesized by atom‐economic reductive cyclocarbonylation of internal alkynes with carbon monoxide catalyzed by [{RhCl(CO)2}2]/CO(NH2)2 in the presence of water (see scheme).
Carbohydrates are slippery customers in water. Camouflaged by solvent‐mimicking hydroxy groups, they make challenging targets, even for natural receptors. In their Communication on page 1775 ff., A. P. Davis and co‐workers describe a synthetic receptor that is remarkably effective for the important β‐N‐acetylglucosaminyl (β‐GlcNAC) unit. The affinities of the receptor are good and its selectivities are excellent, even by the standards of natural carbohydrate‐binding proteins.
Double protection : Efficient Fmoc‐based solid‐phase synthesis (SPPS) of sulfotyrosine (sY) peptides is achieved by incorporating the sY residue(s) as a dichlorovinyl‐protected (DCV) sulfodiester(s) and using 2‐methylpiperidine for Fmoc removal. After removal of the other protecting groups, the DCV group could be cleaved by mild hydrogenolysis giving the sY peptides in good yield.
