Search results for "Total synthesis"

Asymmetric Intramolecular Aza-Michael Reaction in Desymmetrization Processes. Total Synthesis of Hippodamine and epi-Hippodamine

2015

The use of chiral sulfinyl amines both as nucleophilic nitrogen sources and chiral inducers has been described for the first time in a desymmetrization-type process involving an intramolecular aza-Michael reaction. The resulting product was employed as an advanced intermediate in the total synthesis of the natural product hippodamine and epi-hippodamine, taking advantage of the special symmetry of these molecules. In addition, this is the first asymmetric total synthesis of epi-hippodamine.

ChemInform Abstract: Total Synthesis of (+)-Phenguignardic Acid, a Phytotoxic Metabolite of Guignardia bidwellii

2014

(+)-Phenguignardic acid, a phytotoxic metabolite of the grape black rot fungus Guignardia bidwellii was synthesized, as well as its enantiomer, in eight steps from (R)-phenyllactic acid and 3-phenylprop-2-yn-1-ol. The formation of the carboxylate at a late stage, to avoid enolization of the precursor used in the central acetalization step, proved to be crucial. The synthesis of the natural product allowed the unabiguous assignment of its hitherto unknown absolute configuration.

Total Synthesis of (+)-Phenguignardic Acid, a Phytotoxic Metabolite ofGuignardia bidwellii

2013

(+)-Phenguignardic acid, a phytotoxic metabolite of the grape black rot fungus Guignardia bidwellii was synthesized, as well as its enantiomer, in eight steps from (R)-phenyllactic acid and 3-phenylprop-2-yn-1-ol. The formation of the carboxylate at a late stage, to avoid enolization of the precursor used in the central acetalization step, proved to be crucial. The synthesis of the natural product allowed the unabiguous assignment of its hitherto unknown absolute configuration.

Total Synthesis of the Antifungal Natural Product Mollisin

2013

Mollisin, a bioactive polyketide secondary metabolite of the fungus Mollisia caesia, was synthesized in nine linear steps from commercially available 2,6-dimethyl-γ-pyrone. A key transformation in this first total synthesis of mollisin was the ipso substitution of an arylstannane, which permitted the otherwise cumbersome introduction of the characteristic dichloroacetyl moiety. The fungal fungicide was obtained in an overall yield of 9 %.

[2+2+2] Cycloadditions of Alkynylynamides - A Total Synthesis of Perlolyrine and the First Total Synthesis of “Isoperlolyrine”

2011

The total syntheses of the carboline alkaloids perlolyrine and "isoperlolyrine" are reported. Key-steps of the syntheses are Negishi coupling reactions on alkynylynamides and their metal-catalyzed [2+2+2] cycloadditions with nitriles to form the β- and γ-carboline cores. The choice of the catalyst strongly affects the β/γ ratio. Spectroscopic features of the γ-isomer are distinctly different from those of the naturally occurring isoperlolyrine.

A general overview of the organocatalytic intramolecular aza-Michael reaction

2014

The organocatalytic intramolecular aza-Michael reaction gives access to enantiomerically enriched nitrogen-containing heterocycles in a very simple manner. Enals, enones, conjugated esters and nitro olefins have been employed as Michael acceptors, while moderate nitrogen nucleophiles such as sulphonamides, carbamates and amides have been shown to be appropriate Michael donors in this type of reaction. Additionally, the process has been performed under both covalent and non-covalent catalysis, with diaryl prolinols, imidazolidinones, thioureas and chiral binol phosphoric acids being the most frequently used catalysts. The level of efficiency reached with this protocol is demonstrated by the …

Synthesis of (±)-(E)-2,6-dimethyl-6-hydroxyocta-2,7-dienoic acid and the corresponding amide (“acacialactam”)

1994

Abstract The total synthesis of the title compounds in racemic form is described. Linalool was used as the starting material and transformed into the target molecules in 6 steps. The synthetic amide displays spectral properties identical to those reported for the natural compound acacialactam, indicating that the structure proposed for the latter compound is not correct.

Dioncophyllines C2, D2, and F and related naphthylisoquinoline alkaloids from the Congolese liana Ancistrocladus ileboensis with potent activities ag…

2017

Dioncophylline F (1), the first 5,8'-coupled dioncophyllaceous alkaloid (i.e., lacking an oxygen function at C-6 and possessing an R-configuration at C-3), was isolated from the recently described Congolese liana Ancistrocladus ileboensis. Two further, likewise Dioncophyllaceae-type, alkaloids, the dioncophyllines C2 (2) and D2 (3), were identified, along with the Ancistrocladaceae-type compound ancistrocladisine B (4), which is oxygenated at C-6 and S-configured at C-3. The structures of the new compounds were determined by spectroscopic, chemical, and chiroptical methods. The stereostructure of 1 was further confirmed by total synthesis. As a consequence of the lack of a methyl group orth…

Book Review: Classics in Total Synthesis. Targets, Strategies, Methods. By K. C. Nicolaou and E. J. Sorensen

1996

Radiosynthesis of 3-indolyl[1-11C]acetic acid for phyto-PET-imaging: An improved production procedure and formulation method

2014

Abstract An improved production procedure and formulation method for the carbon-11 radiolabeled phytohormone, 3-indolyl-[l- 11 C]acetic acid ([ 11 C]IAA), was developed by modifying selected original reaction parameters. This updated procedure both doubled the yield (from 25.9±6.7% ( n =12) to 61.0±0.3% ( n =10)) and increased the concentration (0.2–0.4 GBq/0.15–0.3 mL), enabling us to provide the radiotracer [ 11 C]IAA suitable for in vivo phyto-PET-imaging studies. The specific activity was improved by more than a factor of three (26.7±5.6 GBq/µmol to 82.5±36.1 GBq/µmol). The total synthesis time for both production and formulation was 81.8±3.0 min ( n =10). In addition, a streamlined sem…