Base-Controlled Synthesis of Heteroatom-Embedded 9-Membered Cycloalkynes and 6-Membered Sultams through Copper-Catalyzed Cyclization.

A facile copper-catalyzed, base-controlled cyclization reaction has been developed for the synthesis of 9-membered cycloalkyne and 6-membered heterocycle sultams under mild conditions. This protocol utilizes a copper-catalyzed intramolecular A (alkyne-aldehyde-amine) coupling reaction to efficiently synthesize 9-membered cycloalkyne sultams in yields up to 90%. Alternatively, by substituting NaHCO with DBU, the protocol achieves selective deprotection of the -propargyl group, thereby facilitating the formation of 6-membered heterocyclic sultams, also in high yields.

The isolation, bioactivity, and synthesis of natural products from with anti-HIV activities.

Natural products isolated from have attracted considerable attention from the chemical community due to their unique structures and promising anti-HIV activities. Recent progresses in the isolation and bioactivity studies for these natural molecules were summarized comprehensively. From the 23 previously uncharacterized compounds isolated from the plant , litseaverticillol B demonstrated the most potent anti-HIV activity , with IC ranging from 2 to 3 μg/mL.

N-Heterocyclic Carbene Catalyzed Reactions Involving Acetylenic Breslow and/or Acylazolium as Key Intermediates.

N-heterocyclic carbene (NHC) organocatalysis has been developed as a powerful tool in modern synthetic chemistry. NHC catalytic activation of ynals and alkynoic acid derivatives provided versatile reactions that involve acetylenic Breslow and/or acylazolium as key intermediates, and diverse transformations have been established for access to molecules with unique skeletons in efficient fashions. Herein we summarize the recent achievements in NHC-catalyzed reactions involving acetylenic Breslow and/or acylazolium intermediates.

Organocatalytic asymmetric synthesis of P-stereogenic molecules.

P-chirality broadly appears in natural and synthetic functional molecules. The catalytic synthesis of organophosphorus compounds bearing P-stereogenic centers is still challenging, due to the lack of efficient catalytic systems. This review summarizes the key achievements in organocatalytic methodologies for the synthesis of P-stereogenic molecules.

Design and Synthesis of Novel Helix Mimetics Based on the Covalent H-Bond Replacement and Amide Surrogate.

A novel hydrogen bond surrogate-based (HBS) α-helix mimetic was designed by the combination of covalent H-bond replacement and the use of an ether linkage to substitute an amide bond within a short peptide sequence. The new helix template could be placed in position other than the -terminus of a short peptide, and the CD studies demonstrate that the template adopts stable conformations in aqueous buffer at exceptionally high temperatures.

Carbene-catalyzed atroposelective synthesis of axially chiral styrenes.

Axially chiral styrenes bearing a chiral axis between a sterically non-congested acyclic alkene and an aryl ring are difficult to prepare due to low rotational barrier of the axis. Disclosed here is an N-heterocyclic carbene (NHC) catalytic asymmetric solution to this problem. Our reaction involves ynals, sulfinic acids, and phenols as the substrates with an NHC as the catalyst.

Carbene-Catalyzed Enantioselective Hydrophosphination of α-Bromoenals to Prepare Phosphine-Containing Chiral Molecules.

Disclosed herein is the first carbene-organocatalyzed asymmetric addition of phosphine nucleophiles to the in situ generated α,β-unsaturated acyl azolium intermediates. Our reaction enantioselectively constructs carbon-phosphine bonds and prepares chiral phosphines with high optical purities. The phosphine products are suitable for transforming to chiral ligands or catalysts with applications in asymmetric catalysis.

Assembly of multicyclic isoquinoline scaffolds from pyridines: formal total synthesis of fredericamycin A.

The construction of an isoquinoline skeleton typically starts with benzene derivatives as substrates with the assistance of acids or transition metals. Disclosed here is a concise approach to prepare isoquinoline analogues by starting with pyridines to react with β-ethoxy α,β-unsaturated carbonyl compounds under basic conditions. Multiple substitution patterns and a relatively large number of functional groups (including those sensitive to acidic conditions) can be tolerated in our method.

Carbene-catalyzed enantioselective annulation of dinucleophilic hydrazones and bromoenals for access to aryl-dihydropyridazinones and related drugs.

4,5-Dihydropyridazinones bearing an aryl substituent at the C6-position are important motifs in drug molecules. Herein, we developed an efficient protocol to access aryl-dihydropyridazinone molecules carbene-catalyzed asymmetric annulation between dinucleophilic arylidene hydrazones and bromoenals. Key steps in this reaction include polarity-inversion of aryl aldehyde-derived hydrazones followed by chemo-selective reaction with enal-derived α,β-unsaturated acyl azolium intermediates.

Total Synthesis of Hoiamide A Using an Evans-Tishchenko Reaction as a Key Step.

The first total synthesis of neurotoxic cyclodepsipeptide hoiamide A () has been accomplished. The synthesis features the use of an Evans-Tishchenko fragment coupling between a five-stereogenic-center-containing β-hydroxyketone and a chiral aldehyde derived from threonine.

Discovery of Amantamide, a Selective CXCR7 Agonist from Marine Cyanobacteria.

CXCR7 plays an emerging role in several physiological processes. A linear peptide, amantamide (1), was isolated from marine cyanobacteria, and the structure was determined by NMR and mass spectrometry. The total synthesis was achieved by solid-phase method.

Total Synthesis of Asperphenins A and B.

The first total synthesis of asperphenins A and B has been accomplished in a concise, highly stereoselective fashion from commercially available materials (15 steps, 9.7% and 14.2% overall yields, respectively).

Direct Oxidation of Aliphatic C-H Bonds in Amino-Containing Molecules under Transition-Metal-Free Conditions.

By employing a simple, inexpensive, and transition-metal-free oxidation system, secondary C-H bonds in a series of phthaloyl protected primary amines and amino acid derivatives were oxidized to carbonyls with good regioselectivities. This method could also be applied to oxidize tertiary C-H bonds and modify synthetic dipeptides.