Synthetic and structural studies on novel gibberellins

Abstract: The structure elucidation of a number of metabolites isolated during biosynthetic studies on gibberellin-like fern antheridiogens from the Anemia genus has been undertaken by synthesising a series of reference samples from gibberellin A7. Two of the metabolites were shown to be the 12p- and 12a-hydroxy derivatives of 9~,15-cyclogibberellin A9 (1) while the 1 lp-hydroxy isomer was identical with a new gibberellin (GAlog) from developing apple seeds. In a cognate study, an efficient total synthesis of this type of gibberellin has baen developed, the key step being the intramolecular cyclopropanation reactions of the aromatic ring in tetralin 2-diazomethyl ketones to give stable norcaradiene products. The [4+2] cycloaddition of selected dienophiles to some of these products allows the rapid stereo-controlled assembly of (1) and related gibberellins