Hydrochloric Acid → Ethyl (2E,4E,6Z,8E)-3,7-dimethyl-9-(2,6,6-trimethylcyclohex-1,4-dienyl)-nona-2,4,6,8-tetraenoate

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(XI where R1, R2, R3, R4 and R5 are methyl, R7 is hydrogen) The crude product IX was dissolved in 5 mL of MeOH, followed by addition of 2 mL of 5N aqueous KOH. The reaction was heated to reflux for 30 min., cooled to 0 ° C., and acidified with 1N aqueous HCl. The product was extracted with EtOAc (3×5 mL), and the combined extract was washed with brine, dried over MgSO4 and concentrated. HPLC purification (C18 -ODS, 65% CH3CN-35% H2O-0.5% AcOH) gave 3.2 Curies of pure 3H2 !-9-cis-retinoic acid XI, specific activity >60 Ci/mmol. TLC (20% EtOAc-hexane) Rf 0.26; UV(MeOH) λmax 343 nm; 1H-NMR (CD3OD) δ 1.05 (s, 1-(CH3)2), 1.48 (t, J=3, 9 Hz, 2-CH2), 1.64 (dtt, J=11, 6, 3 Hz, 3-CH2), 1.71 (s, 18-CH3), 1.98 (s, 19-CH3), 2.04 (t, J=6 Hz, 4-CH2), 2.29 (s, 20-CH3), 5.79 (s, 14-CH), 6.11 (d, J=12 Hz, 10-CH), 6.30 (brd, J=16 Hz, 7-CH+12-CH), 6.70 (d, J=17 Hz, 8-CH), 7.11 (dd, J=12 Hz, 16 Hz, 11-CH); 3H-NMR (CD3OD) δ 1.48 (d, J=3 Hz, 2-C3H), 1.64 (d, J=3 Hz, 3-C3H).

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