R1 R3 H R2 Oh

FIGURE 4.10 Illicinone E (68) and its related prenylated C6-C3 compounds

(p.o.) in mice (three of three) (Okuyama et al., 1993; Nakamura et al., 1996). Compound 115 also exhibited picrotoxin-like convulsion, and its LD50 was 1.46 mg/kg in mice (i.p.) (Yang et al., 1990).

Pseudoanisatin was first isolated as a nontoxic compound from I. anisatum by Lane et al. (1952). The wrong structure of pseudoanisatin was first proposed on the basis of the spectral data (Okigawa and Kawano, 1971), but later was revised as 118 by x-ray crystal structure determination (Kouno et al., 1983). Treatment of 118 with sodium methoxide in methanol gave rise to a trans-lactonisation product 118a, being of special interest, with the unusual inversions at C-4 and C-5. The structure of 118a was unambiguously determined by x-ray crystallographic analysis. The two plausible mechanisms for this base-catalyzed transformation were proposed as shown in Scheme 4.9 (Kouno et al., 1984).

Other pseudoanisatin-type sesquiterpenes, 6-deoxy-pseudoanisatin (120) (Kouno et al., 1988) and 121 (Tanaka et al., 1998), occurred in the seeds, fruits, and leaves of I. anisatum. The structure of 7-deoxy-7-hydroxypseudoanisatin (123a) (Kouno et al., 1991) from the seeds of I. anisatum was first elucidated as pseudoanisatin-type sesquiterpene, and then was revised as 123b and finally corrected as 123 (Figure 4.20), which belongs to the minwanensin type. Other Illicium plants, I. dunnianum, I. tashiroi, and I. merrillianum, elaborated dunnianin (124), 6-deoxydunnianin (126) (Kouno et al., 1988), 3-benzoylpseudoanisatin (119) (Huang et al., 1996), isodunnianin (125)

OH OH

OH OH

C5H5N

C5H5N

C5H5N

C5H5N

SCHEME 4.5 Chemical conversion from illicinone E (68) to p-bromobenzoates 81a and 81b

(Fukuyama et al., 1993), and 1-hydroxy-3-deoxypseudoanisatin (122) (Huang et al., 1999). The structures of these compounds were assigned on the basis of nuclear magnetic resonance spectral data and by comparison with spectral data of pseudoanisatin (118) and dunnianin (124). Schmidt and Peters (1997) reported that dunnianin (124), 7-deoxy-7-hydroxypseudoanisatin (123a), and 3-benzoylpseudoanisatin (119) were isolated from the American star anise, I. floridanum, and their structures were reinvestigated by nuclear magnetic resonance spectroscopic analyses as well as by x-ray crystallographic analysis of dunnianin. As a result, the structures of 119, 124, and 123a were revised as 119a, 124a, and 123b, respectively, which consist of an 11, 3-5-lactone instead of an 11, 14-e-lactone. In comparison of their spectral data, the occurrence of the very large geminal coupling constant (near 20 Hz), accounting for the presence of 5-lactone, and the appearance of H-3 as a doublet (about 5 Hz) with essentially no coupling with H-2, were found to be characteristic of sesquiterpenes having an 11, 3-5-lactone. In light of the spectral data of the other pseudoanisatin-type sesquiterpenes 120, 125, and 126, the structure of isodunnianin (125) and 6-deoxydunnianin (126) should be revised as 125a and 126a. In 1999, the structure of 123b was revised one more time as 123. The 11, 3-5-lactone ring was revised to a 5-lactone closed between C-11 and C-7. The vicinal coupling constant between H-2 and H-3 of about 0 Hz, however, was not agreeable with such a structure. After all, the x-ray crystallographic analysis proved that the structure of 123

'CHH

H3C CH3

H3C CH3

0 0

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