Labda-7,13-dien

All-/ra s-geranylgeraniol and other olefins have been synthesized through the reaction of allylic sulphonyl carbanions (or other functionalized cr sulphonyl carbanions) with Tr-allylpalladium complexes. -Other applications of allylic sulphonyl anions include syntheses of the marine hexaprene mokupalide, nerol and isogeraniol, solanesol, labda-7,14-dien-13-ol, Icr-hydroxy-tachysterolj and certain alkynes, and allylic alcohols. At low temperatures, allylsulphonyl carbanions (91) will undergo y- and well as or-addition to Michael acceptors. The presence of a y-keto-group also promotes y-substitution of allylsulphonyl carbanions. ... 

Biosynthesis. The starting compound is geranyl pyrophosphate (see Terpenes). Acyclic D. are formed by hydrolysis of the pyrophosphate residne (e.g. phytol). Geranylgeranylpyrophosphate is probably converted easily to geranyl linalool, which is then converted to bi- and tricyclic compoimds (Rg.). In a few of the cyclic D-, e. g. abietic acid, there is a migration of the substituents. The gibberellins are derived from the labda-diene type of D. 

Di88 Labda-8( 17), 13-dien-15,12R -olid-19-oic acid T. standishii EBV [125]... 

Fig. (25). Structure of labda-7,13 -dien-2 3-15-diol isolated from Baccharis grisebachii...

Achilladelis and Hanson have studied the incorporation of [2- C,2- H2]-, [2- C,3J ,4R- H]-, and [2- C,5- H2]-mevalonic acid into rosane terpenoids (60). Their results, together with the non-incorporation of pimaradiene, excludes any diene intermediates between (59) and (60). Since labda-8(17),13-diene-15,19-diol... 

The photosensitized oxygenation of 12(Z)-abienol has been studied in a biomimetic synthesis of tobacco labdanoids. In the reaction with singlet oxygen the major process is an ene-reaction involving attack at C-13 and yielding after reduction the 11(H),13(/ and 5)-labda-ll,14-diene-8,13-diols. Some minor products arose from attack at C-12 and include the 12(i )- and 12(5)-labda-13(16)-14-diene-8,12-diols. Reaction of c -abienol with m-chloroperbenzoic acid gave some 8,12- and 8,13-epoxides. The X-ray crystal structure of 12(5),13(S)-8,12 12,15-diepoxy-13-bromolabdane has been determined. The synthesis has been described of some 13,8 13,17-ethers of the enantio-14(15)-dinorlabdane series from eperuic acid. 

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