A highly stereoselective synthesis of 11Z-retinal using tricarbonyliron complex.
A stereoselective synthesis of 11Z-retinal 2, which is the chromophore of visual pigment (rhodopsin), was accomplished from the beta-ionylideneacetaldehyde-tricarbonyliron complex 3. The Peterson reaction of 3 using ethyl trimethylsilylacetate smoothly proceeded to afford predominantly the Z-ester 6. Transformation of the Z-ester 6 to the methyl ketone 19, followed by the Emmons-Horner reaction of 19 with C2-cyanophosphonate, produced ethyl 11Z, 13E-retinonitrile-tricarbonyliron complex 21 as the only product. Decomplexation of 21 with CuCl2 and subsequent DIBAL reduction gave 11Z-retinal 2 in excellent yield. Mechanistic consideration of Z-selectivity in the Peterson reaction of the aldehyde-tricarbonyliron complex is also discussed.
Wada
A
A
Kobe Pharmaceutical University, Japan. a-wada@kobe-pharma-u.ac.jp
Fujioka
N
N
Tanaka
Y
Y
Ito
M
M
D005290:Ferric Compounds / Q000138:chemical synthesis*; D007202:Indicators and Reagents; D009682:Magnetic Resonance Spectroscopy; D012172:Retinaldehyde / Q000138:chemical synthesis* / Q000737:chemistry; D013055:Spectrophotometry, Infrared; D013056:Spectrophotometry, Ultraviolet; D013237:Stereoisomerism; D014801:Vitamin A / Q000737:chemistry*
D005290:Ferric Compounds; D007202:Indicators and Reagents; D014801:Vitamin A; D012172:Retinaldehyde