68330-43-8Relevant articles and documents
Biosynthesis of the off-flavor 2-methylisoborneol by the myxobacterium Nannocystis exedens
Dickschat, Jeroen S.,Nawrath, Thorben,Thiel, Verena,Kunze, Brigitte,Mueller, Rolf,Schulz, Stefan
, p. 8287 - 8290 (2007)
(Chemical Equation Presented) A bouquet of bacteria: Methylisoborneol (1) is a widely occurring volatile from bacteria and an undesirable flavor (off-flavor) in the food industry. The analysis of isotopomers obtained by feeding isotopically labeled precursors to myxobacteria revealed the biosynthetic pathway to 1. Geranylpyrophosphate (CPP) is alkylated by S-adenosylmethionine (SAM) and the product is cyclized to 1. The methylation of GPP is unprecedented in nature.
Dimmel,Fu
, p. 3782,3787 (1973)
Biochemistry and molecular genetics of the biosynthesis of the earthy odorant methylisoborneol in Streptomyces coelicolor
Wang, Chieh-Mei,Cane, David E.
supporting information; experimental part, p. 8908 - 8909 (2009/02/03)
Methylisoborneol (2) is a volatile organic compound produced by a wide variety of Actinomycete soil organisms, myxobacteria, and cyanobacteria. It has an unusually low odor threshold and, together with geosmin, is responsible for the characteristic smell of moist soil as well as unpleasant taste and odor episodes associated with public water supplies and contamination of various foodstuffs, including fish, wine, and beer. Despite considerable interest in detection and remediation of methylisoborneol, the biosynthesis of this methylated monoterpene has been obscure. In Streptomyces coelicolor, the sco7700 and sco7701 genes are shown to correspond to a two-gene operon responsible for methylisoborneol biosynthesis. Both genes have been amplified by PCR and the resulting DNA has been cloned and expressed in Escherichia coli. Incubation of recombinant SCO7701 protein, annotated as a possible C-methyltransferase, with geranyl diphosphate (1) and S-adenosylmethionine gave the previously unknown compound, (E)-2-methylgeranyl diphosphate (3). Incubation of 3 in the presence of Mg2+ with recombinant SCO7700, previously annotated only as a possible metal-binding protein or terpenoid synthase, resulted in the formation of 2-methylisoborneol (2). The steady-state kinetic parameters for both biochemical reactions have been determined. Incubation of geranyl diphosphate and S-adenosylmethionine with a mixture of both SCO7700 and SCO7701 resulted in formation of methylisoborneol (2). Cyclization of 2-methylgeranyl diphosphate (3) to methylisoborneol (2) likely involves the intermediacy of 2-methyllinalyl diphosphate. Copyright
Asymmetric Conversion of Arenechromium Complexes to Functionalized Cyclohexenones: Progress toward Defining an Optimum Chiral Auxiliary
Pearson, Anthony J.,Gontcharov, Alexander V.
, p. 152 - 162 (2007/10/03)
An investigation into the asymmetric synthesis of 5-substituted cyclohexenones via nucleophile addition to (alkoxyarene)chromium tricarbonyl complexes is described. Diastereoselectivity during the nucleophile addition step was achieved using alkoxy substituents derived from terpenoid substrates as chiral auxiliaries. Selectivities as high as 24:1 were obtained when 2-phenylisoborneol was used as the chiral auxiliary and as high as 17:1 using 3,3-(ethylenedioxy)isoborneol. The absolute stereochemistry of the major products was assigned by Mosher's method, after their conversion to the corresponding cyclohexenol. A study of the temperature dependence of the nucleophile addition to alkoxytoluene complexes revealed a thermodynamic preference for addition ortho to the ether substituent.
