Biosynthetic studies with carbon-13: The FT-13C NMR spectra of the sesquiterpenoid coriolins

The Use of Carbon-13 Nuclear Magnetic Resonance Spectroscopy in Natural Products Chemistry

“…The effects of substituents on the shieldings of c:1, ~, Y and 0 carbons are discussed. While on the basis of a simple chemical shift estimate 0, 11.8 is predicted for C-20 of (278), a value of 14.3 ppm was observed, thus emphasizing the importance of the 0 effect exerted by the axial methyl C- 19. Very recently an analysis of the 13C spectra of a number of different triearboeyc1ic ring-C aromatic diterpenoids (301-320) (3,41) and (321)(322)(323)(324)(325)(326) (3) has been presented. Introduction of an equatorial hydroxyl group at C-ll in (278) is found to invoke a 2.6 ppm downfield shift for C-l.…”

“…COOCH, (320) are compiled in Table 14, those for compounds (321)(322)(323)(324) are indicated in the formulae. The data are found to be sufficiently characteristic to allow stereochemical conclusions.…”

Linear Triquinane Sesquiterpenoids: Their Isolation, Structures, Biological Activities, and Chemical Synthesis

“…(−)-Complicatic acid ( 5 ) was first isolated from the fungus Stereum complicatum in 1973 [ 13 ]. 5-Dihydrocoriolin C ( 6 ) was obtained from Coriolus consors (ATCC 11574) [ 14 ].…”

Total synthesis of (.+-.)-pentalenene, the least oxidized neutral triquinane metabolite of Streptomyces griseochromogenes

“…Indeed, Cane and his co-workers found that [UL-13C6] glucose, an in vivo precursor to [ 1,2-13C2]acetyl-CoA, is incorporated into pentalenolactone (7) in a manner fully consistent with a mevalonoid pathway.133 Further, the conversion of [8-3H,12,13-14C]farnesyl pyrophosphate to [7-3H, 14,15-14C]pentalenene with a cell-free synthetase preparation from Streptomyces UC5319 has been studied.13b On this basis, pentalenene is seen to be biogenetically related to other important classes of humulene-derived sesquiterpenes, which include fommanosin,18 the illudoids,19 marasmic acid,20 hirsutic acid,21 and the coriolins. 22 On the second front, the biosynthetic conversion of humulene to the illudoids has long been thought to be carbocation based and to proceed through 12 to the so-called protoilludyl cation (13). 23 In an attempt to mimic this process, Ohfune et al heated exocyclic olefin 14a and the epimeric tertiary carbinols 14b in formic acid.…”

“…In order to engage the second chlorine atom in regiospecific double bond formation, 25 was treated with methylmagnesium available by hydrosilation of 4,4-dimethylcyclopentenone,29 and C12C=C=0 itself was viewed as most attractive because of the established regiospecificity of these reactions.30 Indeed, the intended [2 + 2] cycloaddition proceeded smoothly to furnish 20 in 83% yield. When 20 was subjected to aqueous acidic hydrolysis in order to free the angular hydroxyl group, the anticipated mixture of 22 and hexaethyldisiloxane was obtained. However, the lability of 22 to both chromatography and heat precluded the satisfactory purification of the cyclobutanone.…”