Enantiomerically pure δ- and γ-sultams have been prepared by intramolecular [4+2] cycloaddition of N-1-phenylethyl substituted vinylsulfonamides with purely thermal activation and under high pressure. An optimized procedure for reductive debenzylation of the resultant δ-sultams is also reported.
A new solid-phase method for the synthesis of derivatives of the philanthotoxins is described. Diamines are attached as carbamates to hydroxymethyl polystyrene resin. Selective mono-alkylations by acid-labile, substituted benzhydryl chlorides, followed by reductive alkylations with Fmoc-protected amino aldehydes are employed to assemble the polyamine backbone. Different acid-stability of the benzhydrylic...
The optically pure cyclohexenone core of scyphostatin (1) has been synthesized from cyclohexadiene acetal 5. The crucial aspects of our synthesis include the intramolecular bromoetherification of 5, the SeO 2 oxidation of 7, and the enone formation of 13 to 4 in the final step.
Two different modes of stabilisation of the α-carbocationic centre in the diferrocenylcarbenium ion 4, available from the ferrocenophane 1 by sequential treatment with ferrocenyllithium and tetrafluoroboric acid, are clearly demonstrated by a combination of 1 H NMR and 57 Fe Mössbauer spectroscopies.
Indium(III) triflamide (In(NTf 2 ) 3 ) has been prepared in high yield and has been demonstrated to be an efficient, recoverable catalyst for a range of aromatic electrophilic substitution reactions. When compared to other indium(III) complexes, anomalous reactivities suggest a non-innocent role for the counterion in the studied processes.
Barangcadoic acid A (1) and rhopaloic acids D (5) to G (8), novel terpenoids with RCE protease inhibitory activity, have been isolated from the marine sponge Hippospongia sp. collected in Indonesia. The structures of 1 and 5–8 were elucidated by analysis of spectroscopic data.
A series of (2,2′-bipyridine)platinum(II) complexes covalently tethered to one or two anthracene or naphthalene chromophores was synthesized in high yields. The compounds were equilibrated with pUC19 plasmid and then irradiated at 350 nm. DNA cleaving reactions showed that the complex attached to two anthracene units exhibited the highest photocleavage efficiency, leading to complete conversion of...
A new Pd-catalyzed route to (±)-podophyllotoxin is disclosed. The strategy is based on an efficient organoaqueous reaction that diastereoselectively introduces the C-4 hydroxyl group and the furan ring. Further functionalization led to an iododerivative, which was cyclized under optimized conditions either to the aryltetralin of (±)-podophyllotoxin or to a five-membered ring isomer.
Regioselective anodic α-monofluorination of oxazolidines 1 derived from α-amino acid was successfully carried out. This is the first example of the successful, direct α-fluorination of protected amino acids. Anodic fluorination of methyl N-acetyl pyroglutamate also provided the corresponding α-fluorinated product in moderate yield, while the anodic fluorination of an open-chain α-amino acid, N-(carboethoxy)methylphathalimide,...
A novel seven-membered ring was unexpectedly isolated from the coupling of dithiodiglycolic acid with 2.2 equiv. of N-hydroxysuccinimide, followed by addition of 0.25 equiv. of methyl (4-aminomethyl)benzoate hydrochloride (2) in the presence of 2 equiv. of triethylamine.
Mixtures of BuLi with Mg(OCH 2 CH 2 OEt) 2 and of LiOCH 2 CH 2 OEt with Bu 2 Mg have been studied by 1 H, 13 C and 7 Li NMR spectra and by ( 6 Li, 1 H) HOESY experiments. It is concluded that the two systems are equivalent and give the same product. The HOESY experiments indicate that partial metal–metal interchange...
A study on the addition of boron enolates of methyl ketones to trans α,β-epoxy aldehydes is reported. The reaction proceeds with an excellent anti stereoselectivity, consistent with the Felkin–Ahn model, toward the synthesis of hydroxylated compounds with defined stereochemistry.
Herein we describe a straightforward solid-phase synthesis directed towards the preparation of families of asymmetrically disubstituted furazano[3,4-b]pyrazines by stepwise displacement of the two chlorine atoms in 5,6-dichlorofurazano[3,4-b]pyrazine by nucleophiles. This synthesis has avoided selectivity problems found in solution chemistry.
The reaction of 4-phenyl- or (2-thienyl)-1,2,3-selenadiazoles with 10 equiv. of arylacetylenes leads to the formation of 2,5-diarylselenophenes in moderate to good yields and 1,4-diarylbuta-1,3-diynes as by-products.
The methacrylate ester of geraniol was synthesized using various lipases, such as porcine pancreatic lipase (PPL), Candida rugosa lipase (CRL) and Pseudomonas cepacia lipase (Amano-PS) as catalysts. The effects of reaction parameters such as type and amount of lipase, solvent, temperature and acylating agent on the conversion of geraniol to geranyl methacrylate was studied. The monomer obtained could...
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