[reaction: see text] The first total synthesis of (+/-)-trachyspic acid, a tumor cell heparanase inhibitor, was accomplished based on Cr(II)/Ni(II)-mediated reaction of the aldehyde containing the citric acid moiety and the long-chain triflate, and the relativeconfiguration of this natural product was determined.
Synthesis of Small Combinatorial Libraries of Natural Products: Identification and Quantification of New Long-chain 3-Methyl-2-alkanones from the Root Essential Oil of <i>Inula helenium</i>
L. (Asteraceae)
作者:Niko S. Radulović、Marija S. Denić、Zorica Z. Stojanović-Radić
DOI:10.1002/pca.2466
日期:2014.1
Recently, a potent anti‐staphylococcal activity of InulaheleniumL. (Asteraceae) rootessentialoil was reported. Also, bioassay guided fractionation of the oil pointed to eudesmane sesquiterpene lactones and a series of unidentified constituents as the main carriers of the observed activity.
Rhodium-Mediated Intramolecular C−H Insertion: Probing the Geometry of the Transition State
作者:Douglass F. Taber、Scott C. Malcolm
DOI:10.1021/jo9803434
日期:1998.5.1
The unsymmetrical alpha-diazo ester 1b, derived from the chiral naphthylborneol 5, was cyclized with a set of rhodium carboxylates (L = CF3CO2, CH3CO2, CH3(CH2)(6)CO2, (CH3)(3)CCO2). The ratio of the three major products ((R,R)-3b, (S,S)-3b, 4b) was determined. It was found that the rhodium catalyst derived from pivalic acid gave the highest ratio of 3b:4b. Lowering the temperature of the reaction (L = (CH3)(3)CCO2) increased both the yield and the diastereoselectivity of the cyclization. From these results and from our computational analysis, it is concluded that the ester carbonyl and the rhodium carbenoid are probably syn in the transition state leading to cyclization.