Enantiospecific synthesis of the tricyclic core structure of lippifolianes

An enantiospecific synthesis of the [6.6.3]-tricyclic carbon framework, 2,6,6,9-tetra-methyltricyclo[5.4.0.02,4]undecane, present in the sesquiterpenes lippifolianes and the diterpenes cyclosclareol, metasequoic acids and parguerols, starting from the readily available monoterpene (R)-carvone, is described.

Enantiospecific total synthesis of ent-5-senceioyloxy-10,11-epoxythapsan-10-ol

Enantiospecific total synthesis of optical antipode of the sesquiterpene 5-senecioyloxy-10,11-epoxythapsan-10-ol has been described. (R)-Carvone has been employed as the chiral starting material and a combination of intramolecular alkyation and Criegee fragmentation are employed for intramolecular stereospecific transfer of the chirality. An intramolecular diazoketone cyclopropanation and regioselective cyclopropane ring cleavage reactions have been employed or the creation of the three requisite contiguous quaternary carbon atoms.

Syntheses based on cyclohexadienes. Part 2. Convenient synthesis of 6-alkylsalicylates, 6-alkyl 2,4-dihydroxybenzoate, and 2,5-dialkylresorcinols

A one pot synthesis of 6-alkylsalicylates and 6-alkyl-2,4- dihydroxybenzoates is described. Cycloaddition of 1-methoxycyclohexa-1,4- or 1,3-dienes with alkylpropiolic esters results in the regio-specific formation of 2-alkyl-6-methoxybenzoates. Thus, methyl 2-methoxy-6-methyl benzoate, methyl 2,4-dimethoxy-6-methylbenzoate, methyl 2,5-dimethoxy-6-methylbenzoate, methyl 2-methoxy-4,6-dimethylbenzoate, and ethyl 2-butyl-4,6-dimethoxybenzoate, have been prepared. By making use of this method, the synthesis of two dihydroisocoumarins namely (±)-mellein (12) and (±)-6-methoxy- mellein (14) is described. Employing a similar strategy, a novel route to 2,5-dialkylresorcinols has been developed. Stemphol (24b) and the antibiotic DB2073 (24d) have been synthesized.

Hydrogel-assisted synthesis of nanotubes and nanorods of US, ZnS and CuS, showing some evidence for oriented attachment

By carrying out the reaction of appropriate metal compounds with Na2S in the presence of a tripodal cholamide-based hydrogel, nanotubes and nanorods of CdS, ZnS and CuS have been obtained. The nanostructures have been characterized by transmission electron microscopy and spectroscopic techniques. Evidence is presented for the assembly of short nanorods to form one-dimensional chains.

Synthesis of enantiopure bis-aziridines, bis-epoxides, and aziridino-epoxides from D-mannitol

A practical synthesis of enantiopure bis-aziridines 11 and 15, bis-epoxides 12 and 17, and aziridino-epoxides 27 and 30 is reported using inexpensive d-mannitol as the starting material. The key transformation involves the reductive cleavage of bis-benzylidene acetal 3 to form dimesylate 4, which was further converted to monoazides and diazides followed by reduction, mesylation, and cyclization to furnish the required compounds in good yields.

An enantiospecific approach to thapsanes from R-carvone: synthesis of (−)-thaps-8-en-5-ol†

The first enantiospecific synthesis of a thapsane, containing three contiguous quaternary carbon atoms, is accomplished starting from R-carvone. An intramolecular alkylation and an intramolecular diazoketone cyclopropanation reaction were employed for the stereo- and regiospecific generation of three contiguous quaternary carbon atoms present in the thapsane framework.

Studies directed towards the synthesis of schisanartane and related complex nortriterpenoids: construction of models of the peripheral ABC and FGH segments of rubrifloradilactone C

A conceptually unifying and flexible approach to the ABC and FGH segments of the nortriterpenoid rubrifloradilactone C, each embodying a furo[3,2-b]furanone moiety, from the appropriate Morita-Baylis-Hillman adducts is delineated. (C) 2010 Elsevier Ltd. All rights reserved.

Selective para metalation of unprotected 3-methoxy and 3,5-dimethoxy benzoic acids with n-butyl lithium-potassium tert-butoxide (LIC-KOR): synthesis of 3,5-dimethoxy-4-methyl benzoic acid

The potassium salt of 3-methoxy and 3,5-dimethoxy benzoic acids undergoes deprotonation at the position para to the carboxylate group selectively when treated with LIC-KOR in THF at -78 degrees C and it has been extended to the synthesis of 3,5-dimethoxy-4-methyl benzoic acid. (C) 2000 Elsevier Science Ltd. All rights reserved.