[Br:1][C:2]1[CH2:6][C:5]([C:12](OCC)=[O:13])([C:7](OCC)=[O:8])[CH2:4][C:3]=1[Br:17].[H-].C([Al+]CC(C)C)C(C)C.CC(C)=O.[OH-].[Na+]>C1COCC1.O>[Br:1][C:2]1[CH2:6][C:5]([CH2:7][OH:8])([CH2:12][OH:13])[CH2:4][C:3]=1[Br:17]
Under nitrogen, a stirred solution of 8.7 g (23.5 mmol) of 1,2-dibromo-4,4-di(carboethoxy)cyclopentene (Step 4) in 70 mL of anhydrous THF at -78° C. was treated with 80 mL of diisobutylaluminum hydride (1.5M in toluene) over a 20 minute period. The reaction was allowed to warm to ambient temperature overnight and was slowly treated with 20 mL of acetone followed by 10 mL of 2.5N sodium hydroxide. Water (100 mL) was added and the solution extracted 5 times with ethyl acetate. The combined extracts were washed with brine, dried (Na2SO4), and concentrated in vacuo to give 5.7 g (85%) of 1,2-dibromo-4,4-di(hydroxymethyl)cyclopentene (10 in Synthetic Scheme III) as a colorless oil: NMR (CDCl3) δ 2.20 (s, 2H), 2.50 (s, 4H), 3.70 (s, 4H).
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