Stereoselective Functionalization at C-9 of Retinal: Synthesis of 9-trans-19-Nor-9-haloretinal Analogs.
作者:Tetsuro SHINADA、Kazuo YOSHIHARA
DOI:10.1248/cpb.44.264
日期:——
Stereoselective functionalization at C-9 of retinal based on the use of the C4+X-unit is described. A sequential linkage of C4+X-units (X=Cl, Br, and I) with ylide 8 (C10) and phosphonate 12 (C5)selectively gave 9-trans-19-nor-9-Cl, Br, and I-retinal derivatives.
9-trans-9-Desmethyl-9-fluororetinal analogs were synthesized by the four-components coupling approach. Horner-Emmons olefination of 3 afforded the undesired 2E-isomer 5 which was transformed to 6E-triene 8 via the Stille coupling reaction. Isomerization of 6E-triene 8 with an iodine catalyst proceeded in a highly regioselective manner to give the 6Z-isomer 9. Wittig reaction of 13 derived from oxidation of 9 followed by reduction and oxidation provided 13-cis-9-desmethyl-9-fluororetinal 17. The 13-cis-analog 17 was regioselectively converted to the all-trans-isomer 19 by treatment with trifluoroacetic acid. (C) 1999 Elsevier Science Ltd. All rights reserved.