15423-57-1Relevant articles and documents
Genome mining in streptomyces avermitilis: Cloning and characterization of sav-76, the synthase for a new sesquiterpene, avermitilol
Chou, Wayne K. W.,Fanizza, Immacolata,Uchiyama, Takuma,Komatsu, Mamoru,Ikeda, Haruo,Cane, David E.
supporting information; experimental part, p. 8850 - 8851 (2010/08/21)
The terpene synthase encoded by the sav76 gene of Streptomyces avermtilis was expressed in Escherichia coli as an N-terminal-His6-tag protein, using a codon-optimized synthetic gene. Incubation of the recombinant protein, SAV-76, with farnesyl diphosphate (1, FPP) in the presence of Mg2+ gave a new sesquiterpene alcohol avermitilol (2), whose structure and stereochemistry were determined by a combination of 1H, 13C, COSY, HMQC, HMBC, and NOESY NMR, along with minor amounts of germacrene A (3), germacrene B (4), and viridiflorol (5). The absolute configuration of 2 was assigned by 1H NMR analysis of the corresponding (R)- and (S)-Mosher esters. The steady state kinetic parameters were kcat 0.040 ± 0.001 s-1 and Km 1.06 ± 0.11 μM. Individual incubations of recombinant avermitilol synthase with [1,1-2H2]FPP (1a), (1S)-[1-2H]-FPP (1b), and (1R)-[1-2H]-FPP (1c) and NMR analysis of the resulting avermitilols supported a cyclization mechanism involving the loss of H-1 re to generate the intermediate bicyclogermacrene (7), which then undergoes proton-initiated anti-Markovnikov cyclization and capture of water to generate 2. A copy of the sav76 gene was reintroduced into S. avermitilis SUKA17, a large deletion mutant from which the genes for the major endogenous secondary metabolites had been removed, and expressed under control of the native S. avermitilis promoter rpsJp (sav4925). The resultant transformants generated avermitilol (2) as well as the derived ketone, avermitilone (8), along with small amounts of 3, 4, and 5. The biochemical function of all four terpene synthases found in the S. avermtilis genome have now been determined.
Synthesis of (E,E)-Germacrane Sesquiterpene Alcohols via Enolate-Assisted 1,4-Fragmentation
Minnaard, Adriaan J.,Wijnberg, Joannes B.P.A.,De Groot, Aede
, p. 7336 - 7345 (2007/10/03)
An efficient method has been developed for the synthesis of (E,E)-germacrane sesquiterpene alcohols. The key step in these syntheses involves the enolate-assisted 1,4-fragmentation of properly functionalized perhydro-1-naphthalenecarboxaldehydes with 1 equiv of sodium tert-amylate as base, to give the corresponding (E,E)-germacrane aldehydes. These aldehydes are not very stable, and in situ reduction of the aldehyde function with Red-Al is required to obtain high yields of the desired germacrane alcohols. This procedure has led to the successful synthesis of 15-hydroxygermacrene B (4) and 15-hydroxyhedycaryol (35) from the mesylates 6 and 33, respectively. When KHMDS is used instead of sodium tert-amylate in the fragmentation reaction of 6, isomerization of the initially formed C(4)-C(5) E double bond cannot be avoided and results, after in situ reduction with Red-Al, in the formation of the (E,Z)-germacrane alcohol 24. The 15-hydroxy-(E,E)-germacranes are excellent starting materials for the selective synthesis of the corresponding 4,5-epoxides, which in turn can perfectly well be used in studies on the biomimetic formation of guaiane sesquiterpenes.
