Enantioselective synthesis of (R)-incrustoporin, an antibiotic isolated from Incrustoporia carneola
摘要:
Highly enantiomerically enriched (R)-incrustoporin was enantioselectively synthesized in 43.6% overall yield starting from 4-iodotoluene. The key steps of the synthesis included the asymmetric hydrogenation of 1-(p-tolyl)-1-pentyn-3-one catalyzed by a non-racemic Ru(II) complex and the Pd-catalyzed cyclocarbonylation of so-obtained highly enantiomerically enriched 1-(p-tolyl)-1-pentyn-3-ol. This Pd-catalyzed reaction, whose stereochemical outcome was previously unknown, proceeded with retention of configuration and 2.5% or less racemization. The enantiomeric purities of (R)-1-(p-tolyl)-1-pentyn-3-ol and (R)-incrustoporin were evaluated by HPLC analysis on a Chiralcel OJ column as well as by performing the H-1 NMR spectra of these compounds in a D2O solution which was saturated with alpha- or beta-cyclodextrin, respectively. (C) 1999 Elsevier Science Ltd. All rights reserved.
Palladium-Catalyzed Coupling of Propargylic Carbonates with N-Tosylhydrazones: Highly Selective Synthesis of Substituted Propargylic N-Sulfonylhydrazones and Vinylallenes
An efficient palladium‐catalyzed coupling of propargyliccarbonates (1) with N‐tosylhydrazones (2, 2′) has been carried out. A wide range of propargylic N‐sulfonylhydrazones (3) and multisubstituted vinylallenes (4) can be obtained selectively by using either [PdCl2(CH3CN)2] or [Pd2(dba)3] as catalysts. (dba=trans,trans‐dibenzylideneacetone, dppp=propane‐l,3‐diylbis(diphenylphosphane), Ts=4‐toluenesulfonyl
Rh(III)-catalyzed meta-C-H functionalization reactions are still rare. Herein, we report the first example of Rh(III)-catalyzed meta-C-H alkenylation with disubstituted alkynes directed by a U-shaped nitrile template. Exclusive regio-selectivity has been achieved using unsymmetrical aryl and alkyl-disubstituted alkynes to afford synthetically valuable trisubstituted olefins. Propargyl alcohols are
The first asymmetric propargylic radical cyanation was realized through a dual photoredox and copper catalysis. An organic photocatalyst serves to both generate propargyl radicals and oxidize Cu(I) species to Cu(II) species. A chiral Cu complex functions as an efficient organometallic catalyst to resemble the propargyl radical and cyanide in an enantio-controlled manner. Thus, a diverse range of optically
Divergent Synthesis of Oxa‐Cyclic Nitrones through Gold(I)‐Catalyzed 1,3‐Azaprotio Transfer of Propargylic α‐Ketocarboxylate Oximes: Experimental and DFT Studies
α‐ketocarboxylate oximes, a new type of alkynyl oximes featuring an ester tether, has been explored by taking advantage of gold catalysis. The incorporation of an oxygen atom to the chain of alkynyl oximes led to the formation of two different oxa‐cyclicnitrones. It was found that internal alkynyl oximes with an E‐configuration deliver five‐membered nitrones, whereas terminal alkynyl oximes with an E‐configuration
Photoredox/Copper Dual-Catalyzed Phosphorothiolation of Propargylic Derivatives for the Switchable Synthesis of S-Alkyl, S-Vinyl and S-Allenyl Phosphorothioates
propargylic derivatives from easily accessible [P(O)SH] compounds. This reaction provides a general, mild and versatile procedure to synthesize a variety of synthetically useful S-alkyl, S-vinyl and S-allenyl phosphorothioates selectively from the same set of simple starting materials.