Synthesis of racemic sarkomycin

Chemistry of erythronolide B. Acid-catalyzed transformations of the aglycon of erythromycin B

“…3.5-Diacetyl-10,l 1-anhydroerythronolide B (12).-A 2.0-g amount of the conjugated enol ether 11 was dissolved in 60 ml of hot 0.01 M hydrochloric acid in 1:1 ethanol-water, and the solution was heated at steam-bath temperature for 1.5 hr. The crystalline product obtained from the cooled solution amounted to 1.6 g (77%), mp 202-204°.…”

“…Caled for C25H40O8: C, 64.08; , 8.60;O,27.32. Found: C,63.95;H,8.57;0,27.51. 3.5-Diacetyl-10,ll-anhydro-8-epf-erythronolide B (13).-A 1.0-g amount of 12 was dissolved in 80 ml of 0.1 M hydrochloric acid in 2:1 ethanol-water. The solution was allowed to stand at room temperature for 13 days, then was reduced to approximately one-half volume.…”

“…Caled for C2óH4o08: C, 64.08; , 8.60; O, 27.32. Found: C,64.22;H,8.69;O,27.38. This compound could also be prepared directly from the conjugated enol ether 11 by conducting the hydrolysis in 0.1 M hydrochloric acid and allowing the solution to stand for [11][12][13] days.…”

“…From 3,5-Diacetyl-10,ll-anhydroerythronolide B (12).-A solution of 12 (0.7 g) in 20 ml of anhydrous pyridine was stirred at 0°while a solution of 0.7 ml of thionyl chloride in 5 ml of pyridine was added dropwise. Stirring was continued for 45 min; then the solution was poured onto cracked ice.…”

“…The position of this second double bond was also confirmed by hydrolysis of the conjugated enol ether 11 to the a-,|9-unsaturated ketone 12. The infrared spectrum of 12 showed the ,ß-unsaturated ketone absorption at 1655 cm-1, while the ultraviolet spectrum showed a maximum at 232 µ (e 12,100). The nmr spectrum contained a peak at 1.78 due to the methyl attached to the conjugated double bond, and a doublet at 6.71 due to the conjugated olefinic proton.…”