Synthesis based on cyclohexadienes. Part-27. Synthesis of functionalized tricyclo[5.2.2.0(1,5)]undecanes

A new methodology for the construction of tricyclo[5.2.2.0(1,5)]undecanes is described from indane-4-carboxylic acids. Birch reduction of indane-4-carboxylic acids followed by conjugation and cycloaddition with alpha-chloroacrylonitrile and hydrolysis lead to the tricyclic compounds 36 and 48 which are intermediates in the eremolactone synthesis.

Synthesis of thiolactones using benzyltriethylammonium tetrathiomolybdate as sulfur transfer reagent

An interesting sulfur transfer reaction mediated by benzyltriethylammonium tetrathiomolybdate [(PhCH2NEt3)(2)MoS4] converts omega-halo acid chlorides to the corresponding thiolactones in moderate to good yields in one step. (C) 1997 Elsevier Science Ltd.

Enzymatic resolution of dioxygenated dicyclopentadienes: Enantiopure hydrindanes, hydroisoquinolones, diquinanes and application to a synthesis of (+)-coronafacic acid

A 5, 10-dioxygenated-tricyclo[5.2.1.0(2,6)]decane derivative 6 has yielded to efficient enzymatic resolution to provide a range of chiral building blocks, whose absolute configuration has been determined through a total synthesis of naturally occuring (+)-coronafacic acid. (C) 1999 Elsevier Science Ltd. All rights reserved.

Interesting reaction of 2,2 '-binaphthol with 1,2-dibromoethane: Synthesis of a novel spirodienone

2,2'-Binaphthol 1 reacts with 1,2 dibromoethane in the presence of potassium carbonate to give rise to a novel spirodienone system 3 and its structure has been confirmed by X-ray analysis.

Enantiodivergent total synthesis of microcarpalide from L-tartaric acid

Stereoselective approach for the synthesis of both enantiomers of bio-active decanolactone microcarpalide is described from L-tartaric acid. The synthesis of the key intermediates en route to the natural product is achieved from L-tartaric acid involving the elaboration of gamma-hydroxy amide derived from tartaric acid and ring opening of an epoxide derived from tartaric acid. (C) 2011 Elsevier Ltd. All rights reserved.

Stereoselective total synthesis of (+/-)-tochuinyl acetate and (+/-)-dihydrotochuinyl acetates

Details of the first total synthesis of the marine natural product dihydrotochuinyl acetate is described. Cyclopentenone annulation of p-methylacetophenone via a Claisen rearrangement-Wacker oxidation based sequence generated the cyclopentenone 3, a known precursor for the sesquiterpenes cuparene, laurene, alpha-cuparenone and beta-cuparenones. Conversion of the ketone moiety into a carboxylate followed by stereoselective alkylation and reduction transformed the cyclopentenone 3 into the primary alcohol 19. Birch reduction of the alcohol 19 followed by acetylation furnished (+/-)-dihydrotochuinyl acetate, whereas direct acetylation of 19 furnished (+/-)-tochuinyl acetate. (C) 1998 Elsevier Science Ltd. All rights reserved.

Rearrangement approaches to sesquiterpenes containing multiple contiguous quaternary carbon atoms. Total synthesis of (+/-)-myltayl-8(12)-ene and (+/-)-6-epijunicedranol

Details of the first total syntheses of the sesquiterpenes myltayl-8(12)-ene and 6-epijunicedran-8-ol are described. The aldehyde 13, obtained by Claisen rearrangement of cyclogeraniol, was transformed into the dienones 12 and 18. Boron trifluoride-diethyl ether mediated cyclization and rearrangement transformed the dienones 12 and 18 into the tricyclic ketones 16 and 17, efficiently creating three and four contiguous quaternary carbon atoms, respectively. Wittig methylenation of 16 furnished (+/-)-myltayl-8(12)-ene (11), whereas reduction of the ketone 17 furnished (+/-)-6-epijunicedranol (23).

Regioselective synthesis of bicyclo[4.2.1]nonane-2,8-diones via BF3.Et2O mediated intramolecular diazo ketone insertion reaction

Treatment of the diazo diones 11a-d with boron trifluoride diethyl etherate furnished the bicyclo[4.2.1]nonane-2,g-diones 15a-d in a highly regioselective manner. (C) 1999 Elsevier Science Ltd. All rights reserved.

Spiroannulation of a cyclopentane ring. Synthesis of spiro[4.n](n+5)alk-2-en-1-ones

A methodology based on Claisen rearrangement-Wacker oxidation and intramolecular aldol condensation strategy starting from cyclic ketones leading to spiro[4.n](n+5)alk-2-en-1-ones has been developed. Thus one-pot Claisen rearrangement of the alkyl alcohols 6a-c furnished the aldehydes 8a-c, which on regiospecific oxidation using Wacker conditions generated the keto-aldehydes 9a-c. Finally, intramolecular aldol condensation transformed the keto-aldehydes 9a-c into spiroannulated products 10a-c.

Synthesis and cation binding properties of new bile acid-based crown ethers

A series of bile acid-based crown ethers (7a-c,12 and 13) were easily constructed from readily available precursors. Measurement of association constants (K-a) with alkali metal picrates in CHCl3 showed that azacrown ethers 7a-c and Chola-Cuowns 12 and 13 show greater binding towards Rb+ and K+. The presence of the aromatic moieties showed subtle changes in the binding properties. Insight II minimized structures show very different conformations of aromatic units in 7a-b and 13.

Synthesis based on cyclohexadienes: Part 26 - Total synthesis of some naturally occurring phthalides from Alternaria species

Total synthesis of the naturally occurring phytotoxic phthalides, silvaticol 7, zinniol 5 and the phthalides 1 and 2, is reported from the substrate 16 derived from the Alder-Rickert reaction of 1-methoxy-2-methyl-3-trimethylslyloxycyclohexa-1,3-diene 15 with dimethyl acetylenedicarboxylate.

Synthesis and characterization of some new dimesogenic compounds

We have synthesized four different types of dimesogenic compounds involving the cholesteryl moiety as one of the mesogenic constituents, and have investigated their liquid crystalline properties. The molecular structures of these dimesogens have been confirmed by spectral analyses; they exhibit a rich polymorphism, as revealed by optical microscopic and differential scanning calorimetric observations. The studies show that the mesomorphic behaviour is sensitive to the nature of the terminal alkyl chains, and to the structure of the 'second mesogen' that is attached to the cholesteryl unit through a polymethylene spacer.

Synthesis and vesicle formation from dimeric pseudoglyceryl lipids with (CH2)(m) spacers: pronounced m-value dependence of thermal properties, vesicle fusion, and cholesterol complexation

Eight new dimeric lipids, in which the two Me2N+ ion headgroups are separated by a variable number of polymethylene units [-(CH2)(m)-], have been synthesized. The electron micrograph (TEM) and dynamic light scattering (DLS) of their aqueous dispersions confirmed the formation of vesicular-type aggregates. The vesicle sizes and morphologies were found to depend strongly on the m value, the method, and thermal history of the vesicle preparation. Information on the thermotropic properties of the resulting vesicles was obtained from microcalorimetry and temperature-dependent fluorescence anisotropy measurements. Interestingly, the T-m values for these vesicles revealed a nonlinear dependence on spacer chain length (m value). These vesicles were able to entrap riboflavin. The rates of permeation of the OH- ion under an imposed transmembrane pH gradient were also found to depend significantly on the m value. X-Ray diffraction of the cast films of the lipid dispersions elucidated the nature and the thickness of these membrane organizations, and it was revealed that these lipids organize in three different ways depending on the m value. The EPR spin-probe method with the doxylstearic acids 5NS, 12NS, and 16NS, spin-labeled at various positions of stearic acid, was used to establish, the chain-flexibility gradient and homogeneity of these bilayer assemblies. The apparent fusogenic propensities of these bipolar tetraether lipids were investigated in the presence of Na2SO4 with fluorescence-resonance energy-transfer fusion assay. Small unilamellar vesicles formed from 1 and three representative biscationic lipids were also studied with fluorescence anisotropy and H-1 NMR spectroscopic techniques in the absence and the presence of varying amounts of cholesterol.

Synthesis of chiral bicyclo[4.3.1]decanes via an intramolecular carbonyl ene-reaction

Synthesis of chiral bicyclo[4.3.1]decanes via an intramolecular acid catalysed type II ene reaction of chiral (5-isopropenylcyclohex-2-enyl)acetaldehydes derived from (R)-carvone is described. (C) 1999 Elsevier Science Ltd. All rights reserved.