Yatein

For example, yatein and podophyllotoxin are biosynthesized from matairesinol (Fig. 12.4) [11, 13, 49]. This conversion involves 5-hydroxylation of one of the 3-methoxy-4-hydroxylphenyl (guaiacyl) moieties of matairesinol to give rise to 5-hydroxymatairesinol (thujaplicatin) followed by dual methylation at the 4- and 5-hydroxyls, giving rise to a 3,4,5-trialkoxyphenyl moiety (Fig. 12.4) [11, 13,49],... 

Fig. 12.4 Biosynthetic pathway for lignans with 9,9 -oxygen including yatein and fxsdophyUo-toxin. DP dirigent protein, PLR pinoresinol/laiiciresinol reductase, PrR pinoresinol reductase, and SIRD secoisolariciresinol dehydrogenase...

Sakakibara N, Suzuki S, Umezawa T et al (2003) Biosynthesis of yatein in Anthriscus sylvestris. Org Biol Chem 1 2474-2485... 

This lactone derives from the shikimic acid-cinnamic acid pathway, via oxidative dimerization of coniferyl alcohol. Whereas the presence of yatein itself was not detected in the plants producing steganes, presteganes A and B were isolated in Steganotaenia araliaceae and constitute therefore viable biogenetic precursors [82,83]. 

Racemic yatein 43 was obtained by Michael addition of the anion of piperonaldehyde dithiomethyl acetal to 5/7-furan-2-one (butenolide), followed by trapping of the resulting enolate with 3,4,5-trimethoxybenzyl bromide (see section 3.2.2). This process gave 43 with the desired trans stereochemistry at the butyrolactone. Oxidative coupling of the two... 

A number of biomimetic semi- or total syntheses using an oxidative coupling of a yatein or matairesinol-type intermediate to form stegane or isostegane lignans such as in Fig. (7) have been reported [35,87]. The major contributions will be reviewed in section 3.2.2. 

On the other hand, pure (-)-yatein 43, which was obtained from recrystallization of the optically enriched material furnished by path b, was sequentially converted as above to (+)-isostegane 44 and (-)-stegane 45, the latter being transformed into (-)-steganacin 2 in 61% yield by stepwise bromination, hydrolysis and acetylation [39],... 

Figure 4.9 Biosynthetic steps from matairesinol to yatein as shown by feeding experiments with Anthriscus sylvestris according to Sakakibara et al. (2003).

As indicated above, the methylenedioxy bridge of yatein is formed wifh 4, 5 -dimefhylfhujaplicatin as a substrate. The methylenedioxy bridge of bursehemin is, however, direcfly infroduced at the level of matairesinol prior to the methylation of the 4 -OH group (Sakakibara et al, 2003). 

The stegane lignans are thought to originate biogenetically from the same pathway as the podophyllotoxin lignans, a common precursor being the dibenzylbutyrolactone yatein, Fig. (6) [35]. 

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