A5081328334- Chemical Synthesis and Analysis
- Chemical synthesis and alkaloids
- Catalytic C–H Functionalization Methods
- Radical Photochemical Reactions
- Microbial Natural Products and Biosynthesis
- Click Chemistry and Applications
- Asymmetric Synthesis and Catalysis
- Carbohydrate Chemistry and Synthesis
- Alkaloids: synthesis and pharmacology
- Axial and Atropisomeric Chirality Synthesis
- Various Chemistry Research Topics
- Synthetic Organic Chemistry Methods
- Sulfur-Based Synthesis Techniques
- Natural product bioactivities and synthesis
- Synthesis and Biological Evaluation
- Fluorine in Organic Chemistry
- Synthesis and Catalytic Reactions
- Synthesis and Reactions of Organic Compounds
- Traditional and Medicinal Uses of Annonaceae
- Medicinal plant effects and applications
- Oxidative Organic Chemistry Reactions
- Antimicrobial Peptides and Activities
- Chemistry and Chemical Engineering
- Chemical Reactions and Isotopes
- Chemical Synthesis and Reactions
Brigham Young University
2016-2025
Provo College
2019
Scripps Research Institute
1997-2002
University of South Florida
1987-1993
Full details of a diastereoselective total synthesis the vancomycin aglycon are described. Two key aromatic nucleophilic substitution macrocyclizations with formation 16-membered diaryl ethers were enlisted for sequential CD and DE ring formations, an effective macrolactamization was developed closure 12-membered biaryl AB system, defined order CD, AB, closures permitted selective thermal atropisomerism newly formed systems or their immediate precursors. This indirect control atropisomer...
Due to significant advances in instrumentation, many previously specialized techniques have become “routine” user facilities. However, detailed knowledge held by experts has often not been relayed general users, so they rely on entry-level information, basic principles, and comparison with literature results for data analysis. As a result, major errors the analysis of multiple surface material techniques, including x-ray photoelectron spectroscopy (XPS), appearing scientific literature....
Iminyl radical cyclizations have emerged as important tools for constructing five- and six-membered nitrogen-containing heterocycles. Both aromatic nonaromatic ring systems are readily accessible from a variety of precursors. This short review focuses on recently discovered iminyl cyclizations. Methods that use heat, transition metals, or oxidants to generate the radicals discussed, protocols employing either UV irradiation visible light. Many these newly developed procedures should be quite...
Microwave-promoted iminyl radical cyclizations can be terminated by trapping with TEMPO, affording functionalized adducts. The use of alkynes as acceptors delivers a range 2-acylpyrroles in good yields. Toxic and hazardous reagents, which are frequently employed reactions, not required. O-phenyl oxime ether substrates constructed single step from readily available ketones.
Abstract The synthesis of functionalized nitriles via microwave‐promoted radical fragmentations cyclic O ‐phenyl oxime ethers is reported. A variety traps can be employed, permitting the generation diverse adducts C−O, C−C, C−N, or C−X bond formation. Other salient features include a simple and practical protocol, very short reaction times, avoidance metal catalysts toxic cyanide reagents. utility this method demonstrated by ring‐distortion steroid‐derived substrate.
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTDiastereoselective Total Synthesis of the Vancomycin Aglycon with Ordered Atropisomer EquilibrationsDale L. Boger, Susumu Miyazaki, Seong Heon Kim, Jason H. Wu, Olivier Loiseleur, and Steven CastleView Author Information Department Chemistry The Skaggs Institute for Chemical Biology Scripps Research 10550 North Torrey Pines Road La Jolla, California 92037 Cite this: J. Am. Chem. Soc. 1999, 121, 13, 3226–3227Publication Date (Web):March 19,...
Full details of studies leading to the total synthesis teicoplanin aglycon are provided. Key elements first generation approach (26 steps from constituent amino acids, 1% overall) include coupling an EFG tripeptide precursor common vancomycin/teicoplanin ABCD ring system and sequential DE macrocyclization 16-membered with formation diaryl ether via a phenoxide nucleophilic aromatic substitution o-fluoronitroaromatic (80%, 3:1 atropisomer diastereoselection) followed by 14-membered FG closure...
The first total synthesis of the tetracyclic alkaloid (−)-acutumine is described. Key reactions include an asymmetric ketone allylation mediated by Nakamura's chiral allylzinc reagent, anionic oxy-Cope rearrangement, and Lewis acid-promoted cyclization amine onto α,β-unsaturated dimethyl ketal.
An account of the total synthesis celogentin C is presented. A right-to-left synthetic approach to this bicyclic octapeptide was unsuccessful due an inability elaborate derivatives right-hand ring. In course these efforts, it discovered that mild Braslau modification McFadyen-Stevens reaction offers a useful method reducing recalcitrant esters aldehydes. left-to-right strategy then examined. The unusual Leu-Trp side-chain cross-link present in left-hand macrocycle fashioned via three-step...
Microwave irradiation of O-phenyloximes produces 1-tetralones via N-O homolysis, 1,5-hydrogen atom transfer (HAT), and cyclization a radical intermediate onto an aromatic ring. The HAT step is facilitated by coordination Lewis acid InCl3·H2O to iminyl radical. reaction rapid exhibits broad substrate scope. A larger scale transformation can be performed using conventional heating instead microwave irradiation.
[reaction: see text] Total synthesis of the alkaloid (+/-)-hasubanonine is described. A key feature route generation a phenanthrene intermediate via Suzuki coupling-Wittig olefination-ring-closing metathesis sequence. Conversion into target molecule required six steps including dearomatization by means oxidative phenolic coupling, anionic oxy-Cope rearrangement, and final acid-promoted cyclization. Production an undesired rearranged product in last step could be suppressed moderating acid strength.
An account of the total synthesis tetracyclic alkaloid (−)-acutumine is presented. A first-generation approach to spirocyclic subunit was unsuccessful as a result incorrect regioselectivity in radical cyclization. However, this work spawned second-generation strategy which spirocycle fashioned via radical−polar crossover reaction. This process merged an intramolecular conjugate addition with enolate hydroxylation and created two stereocenters excellent diastereoselectivity. The reaction...
Two complementary sets of conditions for radical additions thiols to terminal ynamides are described. The use 1 equiv thiol affords the cis-β-thioenamide adducts in rapid fashion (10 min) and good dr, whereas employing excess longer reaction times favors trans products.
Crazy cross-links: The first total synthesis of a member the celogentin/moroidin family antimitotic bicyclic peptides features Knoevenagel condensation–radical conjugate addition sequence to install LeuTrp cross-link and an indole–imidazole oxidative coupling fashion TrpHis (see structure). Detailed facts importance specialist readers are published as "Supporting Information". Such documents peer-reviewed, but not copy-edited or typeset. They made available submitted by authors. Please...
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTTotal Synthesis of the Teicoplanin AglyconDale L. Boger, Seong Heon Kim, Susumu Miyazaki, Harald Strittmatter, Jian-Hui Weng, Yoshiki Mori, Olivier Rogel, Steven Castle, and J. Jeffrey McAteeView Author Information Department Chemistry The Skaggs Institute for Chemical Biology Scripps Research 10550 North Torrey Pines Road, La Jolla, California, 92037 Cite this: Am. Chem. Soc. 2000, 122, 30, 7416–7417Publication Date (Web):July 14,...
A new radical-polar crossover reaction was developed that consists of intramolecular conjugate addition an aryl radical followed by enolate formation and hydroxylation. C-C bond, a C-O two congested stereocenters are created in the process. The product is obtained as single isomer. method used to synthesize spirocyclic subunit alkaloid acutumine.
Regioselective base-free intermolecular aminohydroxylations of functionalized trisubstituted and 1,1-disubstituted alkenes employing benzoyloxycarbamate 3a catalytic OsO(4) are described. In all cases, the more substituted alcohol isomer is favored. Sluggish reactions could be promoted by gentle heating, use amine ligands, or increased catalyst loadings. A competitive rearrangement was observed with a secondary allylic substrate. The adducts serve as useful precursors to dehydroamino acids.
The Cinchona alkaloid derived chiral ammonium salt developed by Park and Jew functions as an effective catalyst for the synthesis of β-hydroxy α-amino acids via asymmetric aldol reactions under homogeneous conditions. syn diastereomers are obtained in good ee, aryl-substituted aliphatic aldehydes best substrates reaction. These results represent highest ee's to date direct glycine equivalents catalyzed inexpensive, readily prepared salts.
A synthesis of the hasubanan alkaloids hasubanonine, runanine, and aknadinine via a unified route was attempted. Construction key phenanthrene intermediates by Suzuki coupling−Wittig olefination−ring-closing metathesis sequence allowed convergent flexible approach. Conversion phenanthrenes into target structures projected to involve six steps including phenolic oxidation, ketone allylation, anionic oxy-Cope rearrangement, acid-promoted cyclization. The final step thwarted pinacol-like...
Chiral phase-transfer catalyst 5 containing an electron-deficient trifluorobenzyl moiety promoted the alkylation of glycine derivative 6 with propargyl bromide 7a in good yield and excellent ee. The resulting 8 was converted to 14, central tryptophan residue Celogentin C, two steps, Pd-catalyzed heteroannulation as key transformation. This method promises be efficient route for preparation derivatives possessing substitution on indole ring.
The degradation of vancomycin to a series aglucovancomycin derivatives containing modifications in key functional groups and study their thermal atropisomerism are detailed. In all the cases, selective isomerism DE ring system atropisomers was observed under conditions where CD AB stereochemistries were unaffected. Competitive retro aldol cleavage systems (CD > DE) but could be minimized by choice solvent (DE system) or precluded alcohol protection system). Similarly, competitive main chain...