93804-81-0Relevant academic research and scientific papers
Terpene Cyclizations inside a Supramolecular Catalyst: Leaving-Group-Controlled Product Selectivity and Mechanistic Studies
Zhang, Qi,Catti, Lorenzo,Pleiss, Jürgen,Tiefenbacher, Konrad
supporting information, p. 11482 - 11492 (2017/08/30)
The tail-to-head terpene cyclization is arguably one of the most complex reactions found in nature. The hydrogen-bond-based resorcinarene capsule represents the first man-made enzyme-like catalyst that is capable of catalyzing this reaction. Based on noncovalent interactions between the capsule and the substrate, the product selectivity can be tuned by using different leaving groups. A detailed mechanistic investigation was performed to elucidate the reaction mechanism. For the cyclization of geranyl acetate, it was found that the cleavage of the leaving group is the rate-determining step. Furthermore, the studies revealed that trace amounts of acid are required as cocatalyst. A series of control experiments demonstrate that a synergistic interplay between the supramolecular capsule and the acid traces is required for catalytic activity.
Tailor-made N-heterocyclic carbenes for nanoparticle stabilization
Richter, Christian,Schaepe, Kira,Glorius, Frank,Ravoo, Bart Jan
, p. 3204 - 3207 (2014/03/21)
N-heterocyclic carbenes (NHCs) represent a leading class of ligands in organometallic chemistry, but have been rarely exploited as stabilizers for metal nanoparticles (NPs). We report the first example of NHC stabilized Pd-NPs that demonstrate long term stability. These NHC Pd-NPs were synthesized by a facile ligand exchange protocol using rationally designed long chained NHCs (LC-NHCs). Furthermore, we demonstrate that the surface modification of Pd-NPs results in significant chemoselectivity in a model reaction. The Royal Society of Chemistry 2014.
Synthesis and effect of two new penetration enhancers on the transdermal delivery of 5-fluorouracil through excised rat skin
Hanif, Raja Muhammad,Qineng, Ping,Fenzhu, Muo
, p. 1428 - 1431 (2007/10/03)
The tetrahydrogeraniol (THG) derivative, ethyl-(3,7-dimethyl octyl thio) acetate (EDOTA) was prepared by reacting tetrahydrogeranyl bromide (obtained by reaction of 40% hydrobromic acid and concentrated sulfuric acid) with ethyl 2-mercaptoacetate, while 3,7-dimethyl octyl propionate (DOP) was synthesized by a common esterification reaction by reacting THG with propionic acid in the presence of cyclohexane and concentrated sulfuric acid. The penetration-enhancing effect of the new enhancers were compared with THG and Azone in vitro using excised rat skin in modified Franz-type diffusion cells. 5-Fluorouracil (5-FU), a hydrophilic drug with poor skin permeability was used as a model permeant. Skin samples were pretreated with pure liquid enhancers for 12 h. 5-FU flux through the control and enhancer-treated skin increased linearly with its concentration in the receptor compartment. EDOTA and DOP interacted with the skin rapidly (2 h), and the duration of action is at least 24 h. Significant differences were found in the flux values of 5- FU; EDOTA and DOP enhanced the permeability of the drug about 6-fold and 11- fold respectively. Increased partition coefficient and diffusion coefficient values were obtained by these enhancers. The results suggested that the amount of EDOTA and DOP in the skin, especially in the stratum corneum, may be related to their penetration-enhancing effect.
Preparative Production of Optically Active Esters and Alcohols Using Esterase-Catalyzed Stereospecific Transesterification in Organic Media
Cambou, Bernard,Klibanov, Alexander M.
, p. 2687 - 2692 (2007/10/02)
A novel enzymatic approach to the production of optically active alcohols and esters from racemates is developed.It involves the use of esterase catalyzed transesterifications carried out in biphasic aqueous-organic mixtures.Water-insoluble substrates constitute the organic phase, while the enzyme is located in the aqueous phase.Since the fraction of the latter phase can be made very low, such an arrangement solves the problem of both the competition of an alcohol (the nucleophile) with water in the enzymatic reaction and poor solubility of most organic esters and alcohols in water.By use of porous supports (Sepharose or Chromosorb) filled with aqueous solutions of hog liver carboxyl esterase as a stereoselective catalyst and methyl propionate as a matrix ester, the following optically active alcohols and their propionic esters were produced on a preparative scale: 3-methoxy-1-butanol, 3-methyl-1-pentanol, 3,7-dimethyl-1-octanol, and β-citronellol.To overcome a rather narrow substrate specificity of hog liver carboxyl esterase, a nonspecific lipase from yeast (Candida cylindracea) also was employed as a stereoselective transesterification catalyst.Using an aqueous solution of this enzyme confined to the pores of Chromosorb and tributyrin as a matrix ester, we have prepared gram amounts of the following optically active alcohols and their butyric esters: 2-butanol, sec-phenethyl alcohol, 2-octanol, 1-chloro-2-propanol and 2,3-dichloro-1-propanol (subsequently nonenzymatically converted to optically active propylene oxide and epichlorohydrin, respectively), 6-methyl-5-hepten-2-ol, and 1,2-butanediol.
