17-Dehydroxyholothurin A, a New Sulfated Triterpene Glycoside from Sea Cucumber Holothuna impatiens

A new sulfated triterpene glycoside named as 17-dehydroxyholothurin A 1 was isolated from the sea cucumber Holothuria impatiens. Its structure was elucidated on the basis of spectroscopic data (2D NMR and MS) and chemical evidence. Compound 1 showed cytotoxic activity against cancer cell lines MKN-28, MFC-7, KB, HL-60 and Hep G2 with IC50 values of 1.98, 4.53, 2.01, 4.69 and 2.80×10-6 mol/L, respectively.     

A New Disulfated Triterpene Glycoside from the Sea Cucumber Mensamaria intercedens Lampert

A new disulfated triterpene glycoside named intercedenside B was isolated from the sea cucumber Memsamaria intercedens Lampert.The structure was deduced from the spectral data.     

Asymmetric Total Synthesis of a Diastereisomer A of Tuxpanolide

α-Alkylidene-β-hydroxy butyrolactones have been attractive and challenging targets for organic synthesis in various laboratories because that not only they are rich in skeletal diversity and stereochemistry complexity but also many of them possess quite intriguing and wide biological activities.[1] A novel class of the phytane-type diterpenoid named Tuxpanolide, bearing α-alkylidene-β-hydroxy-γ-butyrolactone skeleton, was isolated from Perymenium hintonii in Central Mexico by Maldonado and co-wokers in 1998.[2] Now we firstly report the efficient strategy of the stereocontrolled total synthesis of a diastereisomer A of Tuxpanolide.     

A New Cycloartane Triterpene Glycoside from Souliea vaginata

Souliea vaginata (Maxim.) Franch. (Ranunculaceae) is widely distributed in the southwest and northwest of China. It possesses anti-inflammatory analgesic functions as a well-known Chinese folk medicine. Its rhizomes or the whole plant are used to treat conjunctivitis, stomatitis, pharyngitis, enteritis, and diarrhea1. Previously, we have reported the isolation and structural elucidation of suolieasides A-C from the ethanol extract of the rhizomes of this plant2. In our further investigation…     

A New Cycloartane Triterpene Glycoside from Soufiea vaginata

A new cycloartane triterpene glycoside was isolated from the rhizome of Souliea vaginata. Its structure was established as 12-deacetyloxy-15α-hydroxy-23-epi-26-deoxyactein by spectroscopic and chemical methods.     

Total Synthesis of N-Methylsansalvamide A

Sansalvamide A is a cyclic depsipeptide, isolated from a marine fungus of the genus Fusarium by Belofsky in 19991. The depsipeptide displays cytotoxic and antiviral activities, and also possesses inhibitor of MCV topoisomerase2. The corresponding amide de…     

Total Synthesis of Przewaquinone A

PrzetvaquinolleA,anaturalortloquinoneisoIatedfromSalviaPrzewakiiMtalmvarmandarinorunIShb.['J.hasbeenshowedanhtumorachvityinaVariety'oftumormodels,sucha5Let`dsIungcarcil1oma,Il1e1anolnaBl6,sarcomal8Oandleuke1niaPss8,bothinvitroandvivo.Inthepresentpaper,h1efirsttota19'11tl1esisofprzett2q[linoneAisdescribed.Targetmoleculeunpreparedtliroughareactionsequence(asshoxvnil1scheme.).Con1pound5ttasobtalnedbycyclizahonof4in56.l%}jeld.Dicarbox})licacid5washeatedwithcoPperPOwderinquinolinetoaffordmo…     

Total Synthesis of Homodimericin A

We report the concise total synthesis of homodimericin A ( 1 ), a recently identified fungal metabolite bearing an unprecedented molecular architecture. The success of the approach hinges on a series of rationally designed and bioinspired transformations, including a Moore rearrangement to assemble the monomeric hydroquinone precursor, homodimerization through double Michael addition to construct the planar A/B/C tricyclic framework, and a tandem Diels–Alder reaction/carbonyl–ene cyclization to forge the congested D/E/F tricyclic cage motif. Unequivocal evidence for the elucidated structure of homodimericin A was also provided by this study.     

Total Synthesis of (−)-Glaucocalyxin A

A practically useful method for the formation of the highly oxygenated bicyclo[3.2.1]octane ring system through Mn(OAc)₃-mediated radical cyclization of alkynyl ketones was developed, which opens up a new avenue for the total synthesis of a number of highly oxidized diterpenoids. Application of this method enabled the first total synthesis of (−)-glaucocalyxin A. Other salient features of the synthesis include a highly enantioselective conjugate addition/acylation cascade reaction, a Yamamoto aldol reaction, and an intramolecular Diels–Alder reaction to assemble the A/B ring system.     

Bioinspired Total Synthesis of Homodimericin A

Homodimericin A is a remarkable fungal metabolite. This highly oxygenated racemic unsaturated polyketide poses a significant synthetic challenge owing to its sterically demanding central cagelike core containing eight contiguous stereogenic centers (including three quaternary stereocenters) and several carbonyl functionalities. On the basis of its proposed biogenetic synthesis, we designed a total synthesis of homodimericin A that proceeds in seven steps and features a double Michael reaction, an intramolecular Diels–Alder reaction, and an ene reaction.     

Asymmetric Total Synthesis of Cephanolide A

The first asymmetric total synthesis of cephanolide A, a complex hexacyclic C₁₈ dinorditerpenoid from cephalotaxus sinensis, was achieved. The synthesis features a convergent strategy, which provides a flexible approach to prepare the biogenetically cephalotaxus diterpenoids and structurally related derivatives for biological studies. A mild intramolecular Prins cyclization was developed to construct the central hexahydrofluorenol skeleton (A-B-C ring), which relies on the originally proposed hydroacylation strategy. A remote hydroxy group directed hydrogenation was applied to stereospecifically reduce the tetra-substituted enone unit. A sequence of ring forming steps, including lactonization, cation mediated etherification and Friedel–Crafts cyclization, was efficiently utilized to forge the cage-like skeleton.     

Total Synthesis of Illisimonin A and Merrilactone A

Illicium sesquiterpenes are a large family of biologically active secondary metabolites isolated from Illicium species of plants and are well-known for their activity of neurite outgrowth in cultured neurons. Herein, we propose a comprehensive biosynthetic pathway for illicium sesquiterpenes and report a synthetic route to illisimonin A and merrilactone A based on it. We think that the carbon scaffolds of most of the illicium sesquiterpenes could be synthesized from a dicarbonyl derivative of allo-cedrane through retro-Dieckmann condensation, oxidative cleavage and aldol reaction at suitable oxidation states in Nature. The common intermediate for illisimonin A and merrilactone A similar to the dicarbonyl derivative of allo-cedrane was assembled with up to 82 % ee by an asymmetric intramolecular desymmetrizing reductive Heck reaction by the use of a new type of chiral phosphine ligand. The syntheses of illisimonin A and merrilactone A supported the key transformations of the proposed biosynthetic pathway.     

Total Synthesis of Antitumor constituent Howiinol A

HowiinolA,anovellaCtoneisolatedftomtheethanchcextractsoftheodallstembaIkofGoniotbamushowilMerr.(Annare)inourl~toryhasboshowntopossesssighficantantitumorachvihestowarhUInantumoreellsinviIIDndinvivoalllesstokidhes1,soitisaveqinterestwCOm~fordevdwiasantitumordrUgS.ffestruanallrelavecondgUraonofhowiin0lAliasbeenestabishedbypetralanalysestObe11.Ih~toPrOvidemereqUalltihesofsamPlef0rbobi0logicalinveshgahon,wehavstudieditSsynthesis.hidrisPaPer,wereportthetotalsynthesisof1fromcr-D-glucoheptoi…     

A New Formal Total Synthesis of β-Elemenone

A short, stereoselective synthesis of an intermediate in Grieco's synthesis of β-elemenone is described.     

A Concise Enantioselective Total Synthesis of (−)-Deoxoapodine

We have established a highly convergent 10-step route for the total synthesis of (−)-deoxoapodine, which is a hexacyclic aspidosperma alkaloid. The quaternary C5 center of the characteristic tetrahydrofuran ring was constructed by a chiral-phosphoric-acid-catalyzed enantioselective bromocycloetherification in a 5-endo fashion and subsequent allylation by using the Keck protocol. Construction of the aspidosperma skeleton features the formation of a nine-membered lactam by a catalytic C−H palladation/alkylation cascade at the indole 2-position and an iron-catalyzed oxidative transannular reaction at a late-stage of the synthesis.     

Total Synthesis of Spiroalkaloids Lycibarbarines A–C

The concise and efficient synthesis of tetrahydroquinoline alkaloids lycibarbarines A−C has been accomplished in four steps from a common intermediate derived from commercially available 2-deoxy-D-ribose and 8-hydroxyquinoline. For the synthesis of the unique tetracyclic spiro-heterocycle skeleton we employed a synthetic strategy that features two key transformations: iodomethyllithium-based homologation of lactone / N-alkylation to access tetracyclic spiro-heterocycle skeleton in one step and one-pot acetonide deprotection, hemiacetal formation, and spirocyclization cascade process.     

A Concise Total Synthesis of S-(+)-Tylophorine

Phenanthroindolizidine alkaloids, which exhibit extensively biological properties, are widely present at various plants of the Asclepiadaceae family.[1] The significantly biological importance of these natural products has attracted considerable synthetic efforts.[2] We herein report an efficiently asyinmetric synthesis of S-(+)-tylophorine (1), as a typically representative alkaloids.     

Total Synthesis of (±)-Celaphanol A

Celaphanol A was a diterpene isolated from the stems of Celastrus stephanotifolius1, which have been the subject of continued and growing interest, due to the range of biological activities shown by many members of this family2. Some have been used in traditional medicine3 or as a stimulant4 from ancient times. In order to further study the relationship between the structure and biological activity of the diterpene compound and as an extension of diterpenoid synthesis in our laboratory5, 6, …     

Total Synthesis of (+)-6-epi-Ophiobolin A

The ophiobolin sesterterpenes are notable plant pathogens which have recently elicited significant chemical and biological attention because of their intriguing carbogenic frameworks, reactive functionalities, and emerging anticancer profiles. Reported herein is a total synthesis of (+)-6-epi-ophiobolin A in 14 steps, a task which addresses construction of the synthetically challenging spirocyclic tetrahydrofuran motif as well as several other key stereochemical problems. This work demonstrates a streamlined synthetic platform to complex ophiobolins leveraging disparate termination modes of a radical polycyclization cascade for divergent elaboration and functionalization.