Diterpenes gibberellins

Diterpenes Gibberellins (D 6.3) Plants (Leaves) Stimulating elongation of shoots... 

Diterpenes Gibberellins (D 6.3) Products of Fusarium monilU forme (Gibberella fujikuroi) and Sphaceloma manihoticola, causing elongation of internodes of rice and cassava plants, respectively, due to interference with the hormone metabolism of the host... 

Dr. Ken ichi Takeda, then Director of Shionogi Research Laboratories, Na-gata extended his research efforts to include the first total synthesis of the diterpene alkaloid group including atisine, garryine, and veatchine as well as the gibberellins all in their racemic form. 

Diterpenes (C20) can be linear as in the phytol part of chlorophyll or mono- to tetracyclic.87 Very well researched are the tricyclic taxanes of which taxol A from the Taxus baccata tree inhibits cell division and has found use in anticancer treatment. Certain labdanes inhibit blood platelet aggregation and kaurane norditer-pene glycosyl ester atractylosides from the Mediterranean thistle block the ATP/ADP translocation - such diterpenes are very toxic when ingested. Ubiquitous plant-derived kaurane-type diterpenes are the plant hormones (gibberellins) or defense substances (phytoalexins). 

Figure 2.12 Structures of diterpenes related to gibberellins. Reprinted with permission of Shokabo Publishing Co., Ltd...

Tripterifordin (26) is an anti-HIV diterpene isolated in 1992 from a Chinese plant Tripterygium wilfordii by Lee and coworkers. Although it is not a plant hormone, its structural similarity with gibberellins attracted me to synthesize it. 

Synthesis of a Veatchine-type Intermediate.—A recent synthesis32 of gibberellin-A15 involves an intermediate of interest for the synthesis of diterpene alkaloids. Enmein (58) had previously been converted to the alcohol (59).33 Oxidation of this alcohol afforded an aldehyde which was converted to its oxime. Removal of the blocking group afforded (60). The nitrone (61), prepared by treatment of (60) with bromonium azide, was photolysed to (62). The resemblance of this intermediate to several alkaloids of the veatchine-type is obvious. Minor variations of this scheme may prove to be of synthetic interest. 

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