Michael Chiang

National Sun Yat-sen University | NSYSU · Department of Chemistry

A known briarane, brianthein W (1), along with four new hydroperoxybriaranes, briaviolides R–U (2–5), have been obtained from the octocoral Briareum violaceum. The absolute configuration of 1 was determined by X-ray analysis for the first time and the structures of briaranes 2–5 were established by spectroscopic methods. Bioactivity study showed th...

A series of 6-membered ring aluminum (Al) complexes bearing Schiff base, benzotriazole phenolate, aminophenolate, carboxamide phenolate, and carboxylate phenolate were synthesized, and their applications in ε-caprolactone (CL) polymerizations were studied. The decreasing catalytic rates for CL polymerization were ranked as follows: Al complexes bea...

A series of Cu complexes bearing N-heterocyclic carbene were synthesized, and their application for the copper-catalyzed azide-alkyne cycloaddition reaction was studied. The catalytic results demonstrated that [L2Cu]Br exhibited the most activity, and the trend of the other complexes was I > Br > Cl ∼ BF4 > PF6. The ¹H NMR spectrum of the reaction...

A series of titanium complexes bearing substituted diphenolate ligands (RCH(phenolate)2, where R = H, CH3, o-OTs-phenyl, o-F-phenyl, o-OMe-phenyl, 2,4-OMe-phenyl) was synthesized and studied as catalysts for the ring opening polymerization of L-lactide and ε-caprolactone. Ligands were designed to probe the role of chelate effect and steric effect i...

A series of dinuclear aluminum (Al2Pyr2) complexes bridged by two pyrazole ligands were synthesized, and their catalytic activity toward ring-opening polymerization of ε-caprolactone (CL) was investigated. Different types of the Al-N-N-Al-N-N skeletal ring were found among these Al2Pyr2 complexes. The butterfly form, L(Thio)2Al2Me4, exerted the hig...

A series of five- and six-membered-ring Al complexes bearing Schiff bases was synthesized and their application to the ring-opening polymerization of ε-caprolactone (CL) was studied. The five-membered-ring Al complexes have been shown to have a significantly higher polymerization rate than six-membered-ring Al complexes (2–3 fold for CL polymerizat...

A series of aluminum (Al) complexes bearing hydrazine-bridging Schiff base and salen ligands were synthesized and investigated as catalysts for the ring-opening polymerization of 3-caprolactone (CL). The introduction of steric bulky groups increases the catalytic activity of the corresponding mononuclear aluminum complex. However, the opposite phen...

β-Diketiminato copper(I) complexes play important roles in bioinspired catalytic chemistry and in applications to the materials industry. However, it has been observed that these complexes are very susceptible to disproportionation. Coordinating solvents or Lewis bases are typically used to prevent disproportionation and to block the coordination s...

Treatment of known complex [Cp2Fe2 (μ-SEt)2(CH3CN)2](BF4 )2 (1(BF4 )2) with 2 equiv of 1,4-bis(isocyanomethyl)benzene (1,4-CNCH2C6H4CH2NC; L1 ) or 4,4′-diisocyanophenyl ether (4,4′-CNC6H4OC6H4NC; L2 ) result in the formation of two new-type diisocyanide complexes [Cp2Fe2 (μ-SEt)2(1,4-CNCH2C6H4CH2NC)2](BF4 )2 (2a(BF4 )2) or [Cp2Fe2 (μ-SEt)2(4,4′-CNC...

A series of titanium (Ti) complexes bearing hydrazine-bridging Schiff base ligands were synthesized and investigated as catalysts for the ring-opening polymerization (ROP) of L-lactide (LA). Complexes with electron withdrawing or steric bulky groups reduced the catalytic activity. In addition, the steric bulky substituent on the imine groups reduce...

A series of Al complexes bearing Schiff base and thio-Schiff base ligands were synthesized, and their application for the ring-opening polymerization of ε-caprolactone (CL) and l-lactide (LA) was studied. It was found that steric effects of the ligands caused higher polymerization rate and most importantly the Al complexes with N,S-Schiff base show...

A series of aluminum complexes bearing amidate ligands, including acylamide, sulfonamide, and aryl carbamate, was synthesized. In addition, the optimization of ring-opening polymerization of ε-caprolactone by using these aluminum complexes as catalysts was studied. Polymerization results revealed that steric bulky groups in anilinyl groups decrease...

A series of Al complexes bearing diphenolate ligands was synthesized and their application for the ring-opening polymerization of ε-caprolactone was studied. Positional variation of the substituent on the aryl ring of the RC∗H(4,6-di-t-butylphenol)2 ligand was shown to have a considerable influence on the catalysis result. Complexes with a ortho-su...

New cembranoids 4-carbomethoxyl-10-epigyrosanoldie E (1), 7-acetylsinumaximol B (2), diepoxycembrene B (6), dihydromanaarenolide I (8), and isosinulaflexiolide K (9), along with 11 known related metabolites, were isolated from cultured soft corals Sinularia sandensis and Sinularia flexibilis. The structures were elucidated by means of infrared, mas...

Previous studies on the ring-opening polymerization of ε-caprolactone using structurally related aluminum complexes as pre-catalysts showed inconsistent trends in the total conversion time. We propose that an induction period for Al complexes for conversion to real catalytic species, Al alkoxide, should be considered because the total conversion ti...

A chemical investigation of Zoanthus kuroshio has yielded two new alkaloids, kuroshines A (1) and B (2). The compounds possess a densely functionalized ring system on the basis of the zoanthamine frames. The structures of 1 and 2 were elucidated through interpretation of spectroscopic methods, especially 2D NMR techniques (COSY, HMQC, HMBC, and ROE...

Chemical investigation of a crinoid Himerometra magnipinna has afforded three anthraquinones (1-3), including one new metabolite, (+)-rhodoptilometrin (1). The structures of these compounds were elucidated on the basis of their spectroscopic data and the absolute configuration of 1 was further confirmed by single-crystal X-ray diffraction analysis....

Parvistones A-E (1-5), five new styryllactones possessing a rare α,β-lactone moiety and a 6S configuration, were isolated from a methanolic extract of Polyalthia parviflora leaves. The structures and the absolute configuration of the isolates were elucidated using NMR spectroscopy, specific rotation, circular dichroism, and X-ray single-crystal ana...

Equisetumone (1), an unprecedented sesquiterpenoid, which possesses a novel 4,5-olide tricyclic trans-caryophyllane skeleton, was isolated from the Equisetum palustre fern. The structure of 1 was established by extensive spectral data analysis. This usual metabolite was probably derived from the caryophyllane class of sesquiterpenes, and a biosynth...

Three pregnane-type steroids, including a new metabolite, 3β-methoxy-5,20-pregnadiene (1) along with two known analogues, 3β-acetoxy-5,20-pregnadiene (2) and 5α-pregna-1,20-dien-3-one (3) were isolated from the soft coral Scleronephthya flexilis. Standard spectroscopic techniques were used to determine the structure of new steroid 1. The absolute s...

One new 5alpha,8alpha-epidioxysterol, 3-acetylaxinysterol (1), along with one known sterol, axinysterol (2), were isolated from a Formosan sponge, Axinyssa sp.. The structures of the compounds were determined by spectroscopic methods and the absolute configuration of 2 was further confirmed by single-crystal X-ray diffraction analysis for the first...

Seven novel withanolides, sinubrasolides A-G (1-7), have been isolated from the cultured soft coral Sinularia brassica. The structures of the new metabolites were determined by extensive spectroscopic analyses, and the absolute configuration of 1 was established by X-ray crystallographic analysis. The cytotoxicities of compounds 1-7 against a limit...

A dibromotyrosine derivative, (1'R,5'S,6'S)-2-(3',5'-dibromo-1',6'-dihydroxy-4'-oxocyclohex-2'-enyl) acetonitrile (DT), was isolated from the sponge Pseudoceratina sp., and was found to exhibit a significant cytotoxic activity against leukemia K562 cells. Despite the large number of the isolated bromotyrosine derivatives, studies focusing on their...

Three novel C19 homolignans, taiwankadsurins D (1), E (2) and F (4), and two new C18 lignans kadsuphilins N (3) and O (5) were isolated from the aerial parts of Taiwanese medicinal plant Kadsura philippinensis. The structures of compounds 1-5 were determined by spectroscopic analyses, especially 2D NMR techniques. The structure of compound 5 was fu...

Three new cembrane-type diterpenoids, flexibilins A-C (1-3), along with a known cembrane, (-)-sandensolide (4), were isolated from the soft coral, Sinularia flexibilis. The structures of cembranes 1-4 were elucidated by spectroscopic methods. The structure of 4, including its absolute stereochemistry, was further confirmed by single-crystal X-ray d...

A new norcembranoidal diterpene, 1-epi-sinulanorcembranolide A (1), and a new cembranoidal diterpene, flexibilin D (2), were isolated from the soft corals, Sinularia gaweli and Sinularia flexibilis, respectively. The structures of new metabolites 1 and 2 were elucidated by spectroscopic methods, and compound 2 was found to significantly inhibit the...

Bioassay-guided fractionation of the root tissue of Reevesia formosana led to isolation of 13 cardenolide glycosides, reevesiosides A-I and epi-reevesiosides F-I. Their structures were determined by means of spectroscopic analysis and single-crystal X-ray diffraction was performed using reevesioside A. Reevesioside A, reevesioside F, and epi-reeves...

The new copper(I) nitro complex [(Ph(3)P)(2)N][Cu(HB(3,5-Me(2)Pz)(3))(NO(2))] (2), containing the anionic hydrotris(3,5-dimethylpyrazolyl)borate ligand, was synthesized, and its structural features were probed using X-ray crystallography. Complex 2 was found to cocrystallize with a water molecule, and X-ray crystallographic analysis showed that the...

Bioassay-guided fractionation of the methanolic extract of the root of Ehretia longiflora (Boraginaceae) afforded eight compounds, ehretiquinone (1), ehretiolide (2), ehreticoumarin (3), ehretilactone A (4), ehretilactone B (5), ehretiamide (6), ehretine (7), and ehretiate (8), together with 12 known compounds (9-20). The relative configuration of...

A novel synthesis of substituted 3,4-dihydroisoquinolin-1(2H)-ones is described. o-Oxiranylmethylbenzonitriles, prepared from isovanillin via five synthetic steps, were treated with NaCN/tetra-n-butylammonium bromide (TBAB) to yield 3,4-dihydroisoquinolin-1(2H)-ones in good yields. This one pot reaction demonstrates the novel and chemoselective nat...

Bioassay-guided fractionation of the roots of Neolitsea daibuensis afforded three new β-carboline alkaloids, daibucarbolines A-C (1-3), three new sesquiterpenoids, daibulactones A and B (4 and 5) and daibuoxide (6), and 20 known compounds. The structures of 1-6 were determined by spectroscopic analysis and single-crystal X-ray diffraction. Daibucar...

Four new nardosinane-type sesquiterpenoids, flavalins E-H (1-4) and two new nornardosinane-type norsesquiterpenoids, flavalins I (5) and J (6), along with five known compounds (7-11) have been isolated from a Formosan soft coral Lemnalia flava. The structures of these compounds were elucidated on the basis of their spectroscopic data. Moreover, the...

The decarbonylation reaction of ferric carbonyl dicationic [Cp(2)Fe(2)(μ-SEt)(2)(CO)(2)](BF(4))(2) [1(BF(4))(2)] carried out in refluxing acetonitrile affords a binuclear iron-sulfur core complex [Cp(2)Fe(2)(μ-SEt)(2)(CH(3)CN)(2)](BF(4))(2) [2(BF(4))(2)] containing two acetonitrile coordinated ligands. The treatment of 2(BF(4))(2) with 2 equiv of t...

The mild, efficient, and environmentally friendly method allows to prepare biologically important flavanones.

X-ray diffraction data for compound 14. CCDC 762722; formula: C22H18O4; unit cell parameters: a 7.8452(8) b 25.285(5) c 18.144(2) beta 96.096(9) space group P21/c. (TIF)

X-ray diffraction data for compound 17. CCDC 762723; formula: C22H16O4; unit cell parameters: a 7.9122(8) b 24.817(5) c 17.8259(16) beta 96.380(8) space group P21/c. (TIF)

RP-HPLC chromatogram of compound 1″. Solvent: 35% v/v aqueous MeOH increasing to 80% in 10 min and subsequently changing back to 35%; flow rate:1 mL/min, λ = 245 nm (TIF)

X-ray diffraction data for compound 8. CCDC 762721; formula: C18H14O6; unit cell parameters: a 6.9461(20) b 30.2804(66) c 7.6340(13) beta 93.752(19) space group P21/c. (TIF)

RP-HPLC chromatogram of compound 4. Solvent: 55% v/v aqueous MeOH increasing to 80% in 10 min and subsequently changing back to 55%; flow rate:1 mL/min, λ = 245 nm (TIF)

RP-HPLC chromatogram of compound 8. Solvent: 55% v/v aqueous MeOH increasing to 80% in 10 min and subsequently changing back to 55%; flow rate:1 mL/min, λ = 245 nm (TIF)

400 MHz 1H NMR spectrum of compound 1″. (TIF)

RP-HPLC chromatogram of compound 1. Solvent: 35% v/v aqueous MeOH increasing to 80% in 10 min and subsequently changing back to 35%; flow rate: 1 mL/min, λ = 245 nm (TIF)

RP-HPLC chromatogram of compound 5. Solvent: 55% v/v aqueous MeOH increasing to 80% in 10 min and subsequently changing back to 55%; flow rate:1 mL/min, λ = 245 nm (TIF)

NP-HPLC chromatogram of compound 15. Solvent: 5% v/v isopropanol in dichloromethane increasing to 17% in 12 min; flow rate:1 mL/min, λ = 245 nm (TIF)

NP-HPLC chromatogram of compound 16. Solvent: 5% v/v isopropanol in dichloromethane increasing to 17% in 12 min; flow rate:1 mL/min, λ = 245 nm (TIF)

NP-HPLC chromatogram of compound 18. Solvent: 5% v/v isopropanol in dichloromethane increasing to 17% in 12 min; flow rate:1 mL/min, λ = 245 nm (TIF)

Zoom of 200 MHz 1H NMR spectrum of compound 3 before crystallization. (TIF)

Zoom of 200 MHz 1H NMR spectrum of compound 5 before crystallization. (TIF)

Zoom of 200 MHz 1H NMR spectrum of compound 8 before crystallization. (TIF)

200 MHz 1H NMR spectrum of compound 9 before crystallization. (TIF)

Zoom of 200 MHz 1H NMR spectrum of compound 9 before crystallization. (TIF)

Zoom of 200 MHz 1H NMR spectrum of compound 13 before crystallization. (TIF)

RP-HPLC chromatogram of compound 3. Solvent: 55% v/v aqueous MeOH increasing to 80% in 10 min and subsequently changing back to 55%; flow rate:1 mL/min, λ = 245 nm (TIF)

RP-HPLC chromatogram of compound 7. Solvent: 55% v/v aqueous MeOH increasing to 80% in 10 min and subsequently changing back to 55%; flow rate:1 mL/min, λ = 245 nm (TIF)

RP-HPLC chromatogram of compound 9. Solvent: 55% v/v aqueous MeOH increasing to 80% in 10 min and subsequently changing back to 55%; flow rate:1 mL/min, λ = 245 nm (TIF)

NP-HPLC chromatogram of compound 12. Solvent: 5% v/v isopropanol in dichloromethane increasing to 17% in 12 min; flow rate:1 mL/min, λ = 245 nm (TIF)

NP-HPLC chromatogram of compound 13. Solvent: 5% v/v isopropanol in dichloromethane increasing to 17% in 12 min; flow rate:1 mL/min, λ = 245 nm (TIF)

NP-HPLC chromatogram of compound 17. Solvent: 5% v/v isopropanol in dichloromethane increasing to 17% in 12 min; flow rate:1 mL/min, λ = 245 nm (TIF)

Zoom of 200 MHz 1H NMR spectrum of compound 4 before crystallization. (TIF)

200 MHz 1H NMR spectrum of compound 5 before crystallization. (TIF)

200 MHz 1H NMR spectrum of compound 6 before crystallization. (TIF)

Zoom of 200 MHz 1H NMR spectrum of compound 6 before crystallization. (TIF)

200 MHz 1H NMR spectrum of compound 13 before crystallization. (TIF)

RP-HPLC chromatogram of compound 6. Solvent: 55% v/v aqueous MeOH increasing to 80% in 10 min and subsequently changing back to 55%; flow rate:1 mL/min, λ = 245 nm (TIF)

NP-HPLC chromatogram of compound 11. Solvent: 5% v/v isopropanol in dichloromethane increasing to 17% in 12 min; flow rate:1 mL/min, λ = 245 nm (TIF)

NP-HPLC chromatogram of compound 14. Solvent: 5% v/v isopropanol in dichloromethane increasing to 17% in 12 min; flow rate:1 mL/min, λ = 245 nm (TIF)

Zoom of 400 MHz 1H NMR spectrum of compound 1″. (TIF)

200 MHz 1H NMR spectrum of compound 3 before crystallization. (TIF)

200 MHz 1H NMR spectrum of compound 4 before crystallization. (TIF)

Zoom of 200 MHz 1H NMR spectrum of compound 5 before crystallization. (TIF)

Zoom of 200 MHz 1H NMR spectrum of compound 7 before crystallization. (TIF)

Zoom of 200 MHz 1H NMR spectrum of compound 7 before crystallization. (TIF)

Zoom of 200 MHz 1H NMR spectrum of compound 14 before crystallization. (TIF)

Zoom of 200 MHz 1H NMR spectrum of compound 4 before crystallization. (TIF)

Zoom of 200 MHz 1H NMR spectrum of compound 6 before crystallization. (TIF)

Zoom of 200 MHz 1H NMR spectrum of compound 6 before crystallization. (TIF)

200 MHz 1H NMR spectrum of compound 7 before crystallization. (TIF)

200 MHz 1H NMR spectrum of compound 8 before crystallization. (TIF)

400 MHz 1H NMR spectrum of compound 9 before crystallization. (TIF)

200 MHz 1H NMR spectrum of compound 14 before crystallization. (TIF)

Zoom of 200 MHz 1H NMR spectrum of compound 15 before crystallization. (TIF)

200 MHz 1H NMR spectrum of compound 18 before crystallization. (TIF)

Zoom of 200 MHz 1H NMR spectrum of compound 13 before crystallization. (TIF)

Zoom of 200 MHz 1H NMR spectrum of compound 14 before crystallization. (TIF)

200 MHz 1H NMR spectrum of compound 15 before crystallization. (TIF)

Zoom of 200 MHz 1H NMR spectrum of compound 16 before crystallization. (TIF)

200 MHz 1H NMR spectrum of compound 17 before crystallization. (TIF)

Zoom of 200 MHz 1H NMR spectrum of compound 15 before crystallization. (TIF)

Zoom of 200 MHz 1H NMR spectrum of compound 16 before crystallization. (TIF)

Zoom 200 MHz 1H NMR spectrum of compound 17 before crystallization. (TIF)

200 MHz 1H NMR spectrum of compound 16 before crystallization. (TIF)

Zoom of 200 MHz 1H NMR spectrum of compound 17 before crystallization. (TIF)

Zoom of 200 MHz 1H NMR spectrum of compound 18 before crystallization. (TIF)

Zoom of 200 MHz 1H NMR spectrum of compound 18 before crystallization. (TIF)

Protoapigenone, a natural flavonoid possessing an unusual p-quinol moiety on its B-ring, is a novel prospective anticancer agent with low toxicity that is currently in development. The first economical, one-step synthesis of protoapigenone from apigenin is described on up to gram scale. 13 new 1'-O-alkylflavone analogs were also synthesized, either...

Mild and environmentally benign methods for the syntheses of flavanones are described. The reaction of o-hydroxyacetophenones (1) and benzaldehydes (2) in water in the presence of DABCO at room temperature gave 3-hydroxy-1-(2-hydroxylphenyl)-3-arylpropan-1-ones (3a–i) as intermediates. Followed by an intramolecular dehydration of the 3a–i with the...

Four new nardosinane-type sesquiterpenoids, flavalins A-D (1-4), have been isolated from the Formosan soft coral Lemnalia flava. The structures of the new metabolites were determined by extensive spectroscopic analysis, and the structure of 2 was confirmed by X-ray diffraction analysis. A plausible biosynthetic pathway to 1 and 2 is proposed. Compo...

Seven sesquiterpenoids, hiiranlactones A-D (1-4), (-)-ent-6α-methoxyeudesm-4(15)-en-1β-ol (5), (+)-villosine (6), hiiranepoxide (7), and one triterpenoid, hiiranterpenone (8), together with 22 known compounds, were isolated from the leaves of Neolitsea hiiranensis (Lauraceae). Their structures were elucidated by spectroscopic analysis and single cr...