All E‐10,20‐methanoretinoylopsin, light‐stable rhodopsin. Synthesis and spectroscopy of all E‐10,20‐methano‐ and all‐E‐retinoyl fluoride and their reaction with bovine opsin

Abstract

In order to obtain a light-stable rhodopsin as a potential candidate for crystallization and structural X-ray analysis, we synthesized and characterized the novel all E-10,20-methanoretinoyl fluoride (2). This retinal analogue has a locked 1 I-cis configuration, preventing the lightinduced 1 I-cis + trans isomerization and binds to opsin by a stable peptide bond rather than a Schiff base. 2 reacted with (methylated) bovine opsin, forming a light-and thermo-stable pigment with Alllax at 390 nm. Its opsin shift (2500 cm-' ) is in the same order of magnitude as that in rhodopsin (2650 cm-I), suggesting that the mechanism for the red shift is not located in the direct vicinity of the chromophore-protein linkage. We also report the first synthesis and characterization of all-E-retinoyl fluoride (lo), which failed to give a pigment on reaction with bovine opsin.

Fluoroalkyl Amino Reagents (FARs): A General Approach towards the Synthesis of Heterocyclic Compounds Bearing Emergent Fluorinated Substituents

“…Since the 1960s till today, the Petrov reagent ( 1a ), the Yarovenko reagent ( 1b ) and the Ishikawa reagent ( 1c ) have been commonly used as selective fluorination agents of compounds containing a hydroxyl moiety, such as alcohols [ 18 , 19 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 ], including hydroxyproline [ 50 , 51 , 52 , 53 ] or carbohydrate derivatives [ 54 ], sulfonic [ 19 ] and carboxylic acids [ 55 , 56 , 57 , 58 ]. Interestingly, carbonyl compounds can also react with FARs to afford difluoromethylated compounds [ 59 ].…”