Oxygenation pattern

8/3-Hydroxyscirpene (Table 1 C15H22O3) (fromE sporotrichioides) is the only known example of 8/3-hydroxylation in the simple trichothecenes. 

13-Epoxytrichothec-9-en-8-ones (Table 2) are often referred to as Type B trichothecenes [Group III on the chemical classification (2), based on ring A chemistry] the remaining simple trichothecenes, without a keto group at C-8, are Type A (Groups I and II of the chemical classification). 

Within a given Fusarium species, variation in the ability to effect 4-hydroxylation or acetylation at positions 3 and 15 is significant, and the classification of some Fusarium strains in the Discolor Section 

---

This has the oxygenation pattern of a Diels-Adder adduct if we convert it to a carbonyl compound. 

A has the same oxygenation pattern as the Robinson aimelation product 374A (frames 117-8). 

The H-NMR spectra of pavines can provide appreciable assistance in structural elucidation. The oxygenation pattern of a pavine may be deduced from a careful examination of the methine (H j) and methylene (H. f) proton absorptions (Ic). In the case of 2,3,8,9 substitution, the abc and def protons furnish two superimposable ABX patterns. A doublet integrating for two protons at the lower field end of the system at approximately 8 4.0 represents the bridgehead protons, Ha and Hj. At 60 MHz, it appears as if these protons are coupled to only one of the neighboring protons (J = 6 Hz) (18,20,25). Furthermore, the geminal hydrogens couple to each other with a coupling constant of 17 Hz (18,20). On... 

Some new diterpenoid oxides have been obtained from Eupatorium jhanii. They are jhanol (12) and its 18-acetate together with jhanidiol (13) and its 18-monoacetate and diacetate. Their structures were established by correlation with manoyl oxide and by an examination of their C n.m.r. spectra. 11/3-Hydro-xymanoyl oxide (14) has been isolated from Juniperus oxycedrus ° A group of new 11-oxomanoyl oxide derivatives (15a—e) has been obtained from Coleus forskohlii (Labiatae). Their oxygenation pattern is reminiscent of that of the tricyclic diterpenoids which have beemobtained from other Coleus species. 

The pharmaceutically very interesting dibenzocyclooctadiene lignans, such as steganacin, steganone and schizandrin8-10, constitute ideal synthetic substrates for this method since they have the required oxygenation pattern. 

Note that many other natural anthraquinone structures are not formed via the acetate pathway, but by a more elaborate sequence involving shiki-mate and an isoprene unit (see page 158). Such structures do not contain the characteristic meta oxygenation pattern, and often have oxygenation in only one aromatic ring (see page 164). 

Initial inspection of the structure of griseofulvin shows the alternate oxygenation pattern, and also a methyl group which identifies the start of the polyketide chain. Cyclization of the Cm poly-( )-keto chain folded as shown allows both... 

Both structures nicely illustrate the different characteristic oxygenation patterns in aromatic rings derived from the acetate or shikimate pathways. With the stilbenes, it is noted that the terminal ester function is no longer present, and therefore hydrolysis and decarboxylation have also taken place during this transformation. No intermediates, e.g. carboxylated stilbenes, have been detected, and the transformation from cinnamoyl-CoA/malonyl-CoA to stilbene is catalysed by the single enzyme. Resveratrol has assumed greater relevance in recent years as a constituent of grapes and wine, as well as other food products, with antioxidant, anti-inflammatory, anti-platelet, and cancer preventative properties. Coupled with... 

Clivojuline (195) (10) represents an unusual structural type since it lacks the 9,10-aromatic oxygenation pattern, which is ubiquitious among the other lactone alkaloids. The structure of the related alkaloid cliviahaksine (196) was assigned on the basis of spectral comparisons with 195 although its stereochemistry was not specifically indicated (15). Since cliviaaline (197) was isolated in only very small amounts, its structure was deduced principally from its IR spectrum and its mass spectral fragmentation pattern however, the possibility that it was an artifact was not rigorously excluded (14). 

Isocolchicine, having a reversed oxygen pattern in the tropolonic moiety, and colchicide, lacking the methoxy group in the C-ring, are both inactive. 

These four alkaloids have the same aromatic oxygenation pattern as decodine (6) and nesodine (5). The methoxylation pattern of verticillatine was established in the same way as described for decodine. Enantiomerism of the dimethyl ethers of dihydroverticillatine (25) and decodine at C-5 was demonstrated by a parallel series of degradations to. V-nitroso derivatives... 

Degradation of decodine derived from [3-14C]phenylalanine showed that 58% of the label was located at C-13 and 33% at C-l. Thus, there is a close correspondence of the origins of the two lactonic biphenyl alkaloids of different stereochemistry at C-5 and with different oxygenation patterns. 

---