3594bromo silyl ether 1Sb): 11-cis-loa (23.4 mg, 5.4%), 1 l-cis,l3-cis-l2a J . Am. Chem. SOC. 1983, 105, 3594-3600 Grant EY-02452 and NCI Contract CP-05715) Drovided financial (43.4 mg; lo%), IS%), and 9-cis,llcis-lla (29.6 mg, 6.8%).12,20-Tetramethyleneretinals lob, 1 lb, 12b, and 13b. General Procedure. The seven-membered ring 12,20-tetramethyIeneretinals were prepared by MnOz oxidation of the corresponding retinols according to the procedure described for the six-membered-ring 12,20-trimethyleneretinals 7b. Sb. and 9b. The four seven-membered-ring isomers 1 l-cis-support for this project. ) for 500-MHz spectra, and BASF (Ludwigshafen) for chemicals. Finally, we remain most grateful to Professor R o b e r t R. Birge of this delob, 9-cis,i l-cis-llb, l l-cis,l3-cis-l2b, and 9-cis.1 l-cii13-cis-13b were partment for informative discussions. prepared in yields ranging from 50 to 80%.Preparation of Cyclized Product 29: Thermolyses of 12,20-Tetramethylene-9-cis,ll-cis-retinol ( l l a ) and -9-cis,ll-cis,l3-cis-retinol (13s). The 9-cis,ll-cis-isomer l l a (-2 mg) in freshly distilled hexanes (10 mL) was added under argon to a refluxing solution of hexanes (100 mL). Aliquots were removed at various time intervals and analyzed by high-pressure LC (Waters p-porasil column, 15% ethyl acetate/skellysolve B). Essentially quantitative conversion of the retinol l l a to the cyclized product 29 was complete in -3 h. By contrast, the 9-cis,ll-Registry No.
