Iodine → Spinosyn B

Participants

Reaction Conditions

Reaction Steps

A suspension of Spinosyn A (5.0 gms, 5.13 mmol) and sodium acetate trihydrate (4.68 gms, 34.4 mmol) in 80% methanol/water (125 ml) was heated to 47° C. under nitrogen. The pH dropped from 10 to 8 on addition of iodine (1.75 gms, 68.0 mmol) as a solid in one portion, giving a brown color. The pH was maintained at 8-9 by periodic addition of 1N sodium hydroxide. The reaction was heated for 2.75 h (during which time the color faded to pale yellow), and was then cooled to ambient temperature. The solution was poured into a solution of water (250 ml) and ammonium hydroxide (50 ml), and extracted with diethyl ether. The ether extract was washed with brine, dried (K2CO3), and evaporated at ambient temperature under vacuum. The crude product was purified by reversed phase HPLC on a C18 column, eluting with methanol:acetonitrile:0.05% ammonium acetate (45:45:10) giving Spinosyn B (2.52 gms) which was identical (MS, 1H NMR, 13C NMR, IR, and OR) to a naturally produced sample of Spinosyn B.

Provenance & Evidence