Azadirachtin b(SH) → Azadirachtin

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Reaction Steps

The fractions around the two maxima were constituted by, in all, 8 portions. 15.5 g. azadirachtin A fraction, as well as 8.3 g. azadirachtin B fraction, were obtained. However, the azadirachtin A fraction still contained a large amount of azadirachtin B, whereas the azadirachtin B fraction still contained other substances in almost the same amount as azadirachtin B. Preparative HPLC was used in order to separate azadirachtin A and B. For this purpose, there was used a Latek column filled with silica gel-RP-18 material with a length of 540 mm. and an internal diameter of 54 mm. The separation was optimised. The flowthrough rate was 55 ml./minute with methanol/water (43:57 v/v) as elution agent. For each run, about 5 g. of the azadirachtin A fraction from the column chromatography on silica gel-RP-8 were applied to the column. Every 9 minutes, the receiver was changed at a volume of about 500 ml. The maximum of azadirachtin A was eluted after 284 minutes and the maximum of azadirachtin B appeared after 397 minutes. FIG. 2 of the accompanying drawings shows a preparative HPLC chromatography of the azadirachtin A fraction in the case of chromatography on RP-8. Pure azadirachtin A and azadirachtin B was only contained in the fractions round the peak maximum. Five further azadirachtins were also separated on a smaller scale in side fractions of the preparative HPLC with thin layer chromatography or semi-preparative HPLC. The various azadirachtin derivatives were prepared from azadirachtin A and azadirachtin B.

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