20 J. Org. Chem. 8.10. Found C, 68.65; H, 8.39.4@-(2,5@,6,6-Tetramet hyl-2-cyclohexenyl)-3( E)-buten-&one (2a,. The ketone 18a (35 mg, 0.09 mmol) in dry THF (3 mL) was added to MeONa (30 mg, 0.57 mmol) dissolved in t-BuOH (6 mL) at 5 OC under N2. The mixture was stirred a t room temperature for 7 h. The usual workup and chromatography (SiOz, benzene-AcOEt (101)) provided 2a (16 mg, 86%) as a colorless oil. The synthetic 2a was homogeneous on VPC 4+3m, 170 "C), and ita IR and NMR spectra were superimposable with those of the authentic sample (Shinetsu). Similarly, 1 and 2b were prepared from 17 and 18b in 84 and 85% yield, respectively. The published spectral data of 1,2a, and 2b were in 1980,45, 20-24 agreement with those of the synthetic sample^.'^
RegistryThe chemistry of aloe-emodin (3) has been explored with a view toward its use as a synthon for the regioepecific synthesis of adriamycin and analogues of it. Routes for satisfactory large-scale monomethyl ether formation at CB (4) and regiospecific introduction of a phenolic oxygen function a t C4 (21) are described. Interesting side reactions were encountered, including an apparent peri 0 to 0 acyl wandering reaction during methylation and a reductive debromination reaction during displacement of an aryl bromide by methanolic methoxide.Aloe-emodin (4) has been converted in six steps to 1,4,5-trihydroxy-2-(2,3-dicarboxypropyl)-9,lO-ant~aquinone (17), a synthon suitable for further regiospecific elaboration into daunomycin-adriamycin analogues. A method for Friedel-Crafts acylation of anthraquinones by reduction to the anthracenone, cyclization, and reoxidation has been developed as a key feature of the synthesis.