Sesterterpenes and phenolic alkenes from the Thai sponge Hyrtios erectus

Sesterterpene, erectusolide A (1), six phenolic alkenes, erectuseneols A?F (2–7) and nine known compounds, luffalactone (8), luffariolide E (9), (6E)- and (6Z)-neomanoalide 24,25-diacetates (10 and 11), 6,6-dimethylundecane-2,5,10-trione (12), threo- and erythro-cavernosines (13 and 14), (4E,6E)-dehydromanoalide (15), echinoclerodane A (16), were isolated from the marine sponge Hyrtios erectus. Compound 13 was isolated for the first time from a natural source. The structures of these compounds were elucidated on the basis of spectroscopic analysis. The phenolic alkenes 3 and 7, the sesterterpenes 8–11 and 15, and compounds 12–14 were evaluated for cytotoxic activities against six cancer cell lines, MOLT-3, HepG2, HeLa, HuCCA-1, A549, and MDA-MB-231.     

Mono- versus bis-chelate formation in triazenide and amidinate complexes of magnesium and zinc

Magnesium and zinc complexes of the monoanionic ligands N,N'-bis(2,6-di-isopropylphenyl)triazenide, L1, N,N'-bis(2,6-di-isopropylphenyl)acetamidinate, L2, and N,N'-bis(2,6-di-isopropylphenyl)tert-butylamidinate, L3, have been synthesized, but only L3 possesses sufficient steric bulk to prevent bis-chelation. Hence, the reaction of L1H with excess ZnEt2 leads to the isolation of (L1)2Zn, 1; L1H also reacts with Bu2Mg in Et2O to afford (L1)2Mg(Et2O), 2. Similar reactivity is observed for L2H, leading to the formation of (L2)2Zn, 3, and (L2)2Mg, 4. The reaction of L2H with ZnR2 may also afford the tetranuclear aggregates {(L2)Zn2R2}2O, 5 (R=Me) and 6 (R=Et). By contrast, the tert-butylamidinate ligand was found to exclusively promote mono-chelation, allowing (L3)ZnCl(THF), 7, [(L3)Zn(micro-Cl)]2, 8, (L3)ZnN(SiMe3)2, 9, (L3)MgiPr(Et2O), 10, and (L3)MgiPr(THF), 11, to be isolated. X-ray crystallographic analyses of 1, 2, 3, 4, 5, 6, 8, and 10 indicate that the capacity of L3 to resist bis-chelation is due to greater occupation of the metal coordination sphere by the N-aryl substituents.     

Cerebrosides and a monoacylmonogalactosylglycerol from Clinacanthus nutans

A mixture of nine cerebrosides and a monoacylmonogalactosylglycerol were separated from the leaves of Clinacanthus nutans. The structures of the cerebrosides were characterized as 1-O-beta-D-glucosides of phytosphingosines, which comprised a common long-chain base, (2S,3S,4R,8Z)-2-amino-8(Z)-octadecene-1,3,4-triol with nine 2-hydroxy fatty acids of varying chain lengths (C(16), C(18), C(20-26)) linked to the amino group. The glycosylglyceride was characterized as (2S)-1-O-linolenoyl-3-O-beta-D-galactopyranosylglycerol. The structures were established on the basis of the spectroscopic data and chemical reactions.     

Merrifield resin-supported chain transfer agents, precursors for RAFT polymerization

The modification of Merrifield resins to form chain transfer agent (CTA) precursors for reversible addition fragmentation chain transfer (RAFT) polymerization is investigated. A series of CTA precursor resins were prepared and characterized by FTIR and elemental analysis (EA). [reaction: see text]     

Chromones from the branches of Harrisonia perforata

Four new chromones, perforamone A, B, C, and D have been isolated together with six known compounds, peucenin-7-methyl ether, O-methylalloptaeroxylin, perforatic acid, eugenin, saikochromone A and greveichromenol, from the branches of Harrisonia perforata (Simaroubaceae). The structures were identified by spectroscopic data. The compounds were tested for antimycobacterial and antiplasmodial activities.     

Chemical constituents of the roots of Piper sarmentosum

Sixteen compounds were isolated from the fresh roots of Piper sarmentosum. Seven of these have been previously isolated from the fruits and leaves of this plant: the aromatic alkene (1), 1-allyl-2-methoxy-4,5-methylenedioxybenzene (4), beta-sitosterol, pyrrole amide (6), sarmentine (10), sarmentosine (13) and pellitorine (14). (+)-Sesamin (2), horsfieldin (3), two pyrrolidine amides 11 and 12, guineensine (15) and brachystamide B (16) are new for P. sarmentosum. Sarmentamide A, B, and C (7-9) are new natural products. Compounds 1--4 and 6--16 were tested for antiplasmodial, antimycobacterial and antifungal activities.     

A new dihydrobenzofuran lignan and potential α-glucosidase inhibitory activity of isolated compounds from Mitrephora teysmannii

A new dihydrobenzofuran lignan, (2R,3S)-2-(3′,4′-dimethoxyphenyl)-5-(3-hydroxypropyl)-7-methoxy-2,3-dihydrobenzofuran-3-methyl acetate, named as mitredrusin (1), was isolated from the leaves of Mitrephora teysmannii (Annonaceae) together with 12 known compounds including a related dihydrobenzofuran lignan: (?)-3′,4-di-O-methylcedrusin (2), four polyacetylenic acids: 13(E)-octadecene-9,11-diynoic acid (3), 13(E),17-octadecadiene-9,11-diynoic acid (4), octadeca-9,11,13-triynoic acid (5) and octadeca-17-en-9,11,13-triynoic acid (6), five lignans: (?)-eudesmin (7), (?)-epieudesmin (8), (?)-phillygenin (9), magnone A (10) and forsythialan B (11) and two megastigmans: (3S,5R,6S,7E,9R)-7-megastigmene-3,6,9-triol (12) and annoionol A (13). The chemical structures of these compounds were established on the basis of their 1-D and 2-D NMR spectroscopic data. All compounds were evaluated for their α-glucosidase inhibitory activity. Among these isolates, polyacetylenic acids 3 and 4 showed more than 20-fold much higher activity compared with that of the antidiabetic drug acarbose.     

Synthesis of poly(ethylene adipate) and poly(ethylene adipate-co-terephthalate) via ring-opening polymerization

Syntheses of poly(ethylene adipate) (ROP-PEA) and poly(ethylene adipate-co-terephthalate) (ROP-PEA-co-PET) were achieved via ring-opening polymerization of corresponding cyclic oligoesters. In case of ROP-PEA, cyclic oligo(ethylene adipate) (C-OEA) was equilibrated in the presence of di-n-butyltin oxide as a catalyst under high-concentration conditions at 180 and 200 °C for 1-24 h. The polymer products were obtained in yields up to 100% with the and in the ranges of 3000-23 000 g/mol and 5000-60 000 g/mol, respectively. The ROP-PEA-co-PET was prepared by equilibrating an equimolar amount of C-OEA and cyclic oligo(ethylene terephthalate) (C-OET) using di-n-butyltin oxide catalyst under high-concentration conditions at 250 °C for 24 h. The copolyester produced was obtained in yield of 97% with the and of 18 000 and 46 000 g/mol, respectively. ¹H NMR spectrum of ROP-PEA-co-PET showed two new proton signals of ethylene unit representing the existence of heterolinkage with different chemical environment in the copolymer. This indicated the random transesterification of C-OEA and C-OET resulting in random structure in copolyester. In addition, the result of ROP-PEA-co-PET from DSC showed the glass transition temperature in the values of −8 °C with no melting temperature indicating thermoplastic elastomeric behavior.     

Pyrazine nucleoside analogs. Synthesis and reactions of some 5-thio-substituted pyrazines

5-Benzylthio-1,2-dihydro-2-oxopyrazine ( 8 ) was prepared from 2-amino-5-bromopyrazine by sequential treatment with sodium thiobenzylate and diazotization. Condensation of the silyl derivative of 8 with a protected 2-deoxyribofuranosyl chloride gave α and β anomers of 5-benzylthiopyrazine nucleosides. Reaction of 2,5-dichloropyrazine 4-oxide with sodium thiobenzylate followed by hydrolysis gave 5-benzylthio-1,2-dihydro-2-oxopyrazine 4-oxide ( 16 ).     

Macromolecular design via reversible addition–fragmentation chain transfer (RAFT)/xanthates (MADIX) polymerization

Among the living radical polymerization techniques, reversible addition–fragmentation chain transfer (RAFT) and macromolecular design via the interchange of xanthates (MADIX) polymerizations appear to be the most versatile processes in terms of the reaction conditions, the variety of monomers for which polymerization can be controlled, tolerance to functionalities, and the range of polymeric architectures that can be produced. This review highlights the progress made in RAFT/MADIX polymerization since the first report in 1998. It addresses, in turn, the mechanism and kinetics of the process, examines the various components of the system, including the synthesis paths of the thiocarbonyl‐thio compounds used as chain‐transfer agents, and the conditions of polymerization, and gives an account of the wide range of monomers that have been successfully polymerized to date, as well as the various polymeric architectures that have been produced. In the last section, this review describes the future challenges that the process will face and shows its opening to a wider scientific community as a synthetic tool for the production of functional macromolecules and materials. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43:5347–5393, 2005