Tutin biosynthesis

H2 mevalonate label located at C-8 in (4.81) , five out of the six labels were retained]. A 1,2-shift of hydrogen was excluded in tutin biosynthesis, 2-transr rather than 2-m-farnesol is a precursor for dendrobine (4.81) and further results show that it is the farnesol (l-/ ro-/ )-hydrogen atom which migrates to C-8 in (4.81). The deduced pathway to dendrobine and related sesquiterpenes is summarized in Scheme 4.16 (cf. Scheme 4.17) [85-88]. 

Finally, Jommi et al. addressed the question of the hydrogen shift following the ring closure of famesyl diphosphate to the cyclodecadiene within the biosynthesis of tutin (11) (232). 

Yokoyama J, Suzuki M, Iwatsuki K, Hasebe M (2000) Molecular Phylogeny of Coriaria with Special Emphasis on the Disjunct Distribution. Mol Phylogen Evol 14 11 Corbella A, Gariboldi P, Jommi G, Scolastico C (1969) Biosynthesis of Tutin. J Chem Soc, Chem Conunun 634—635... 

In the biosynthesis of tutin (57) the involvement of copaborneol (56) has been demonstrated. As expected, only one tritium atom was incorporated from [2- C,3R,4R- H]mevalonate. Unfortunately, it is still not clear whether the biosynthesis involves a cadinene system or a germacrene system. The cadinene sesquiterpene, y-muurolene (58), and caryophyllene (59) are formed in Mentha piperitaf The labelling of the latter terpenoid (% from [2- C]mevalonate... 

Earlier experiments on the biosynthesis of tutin (28) with [2- C]mevalonic acid and [2,2- Hj,2- C]mevalonic acid had indicated its sesquiterpenoid nature and had suggested that it was formed via copabomeol (27). Specifically tritiated copabomeol has now been shown to be converted into tutin (28) by Coriaria japonica without randomization of the label. The initial step in the cyclization to form copabomeol has been regarded as the cyclization of the electrophilic C-1 of famesyl pyrophosphate with the distal double bond to form a germacrane cation (26). In order for cyclization to proceed further the reactive centre must then be transferred from C-11 to C-1. One proposal involved a double 1,2-hydride shift from C-10 to C-11 and C-1 to C-10. However, this... 

Experimental verification for the proposed 1,3-hydrogen rearrangements above has recently been obtained in the biosynthesis of avocettin (cadinene-based sesquiterpene) (109), sativene (109), longifolene (109), dendrobine (derived from copaborneol) (20, 140), tutin (derived from copaborneol) (176,177), and culmorin (derived from longiborneol) (178). 

Corbella, A., P. Gariboldi, and G. Jommi Biosynthesis of Tutin from (4R)-[4- Hi]Mevalonic Acid. Chem. Commun. 1972, 600. 

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