Synthetic studies on lycoridicine. II. An effect route to cis dihydrolycoricidine.

The tricyclic skeleton of lycoricidine has been prepared by a route involving an intramolecular [4 + 2]cycloaddition of a trimethylsilyloxydienamide.     

[MESITYL]BACTERIORHODOPSIN. THE PROPERTIES OF AN ANALOGUE OF THE PURPLE MEMBRANE CONTAINING [MESITYL] RETINAL AS THE CHROMOPHORE

Abstract— A new synthesis of all-trans-[mesityl]retinal, II , (all-trans-3,7-dimethyl-9-(2',4',6'-trimethylphenyl)-2,4,6,8,-nonatetraenal) and 13-cis-[mesityl]retinal, VI , (3,7-dimethyl-9-(2'4'6'-trimethylphenyl)-2Z,4E,6E,8E-nonatetraenal) is reported. Combination of all-trans-[mesityl]retinal with bacterioopsin results in the formation of a synthetic membrane (Λ_max 460) which has photocycling properties similar to the purple membrane although its cycling rate is very much slower. An M-type intermediate can be trapped at -60°C. Photoreversal of the M-intermediate to the wavelength of initial absorption is observed. Phototransformation of the initial [mesityl]bacteriorhodopsin is accompanied by conversion of the all-frans to the 13- cis -isomer.