Pyxinic acid

Yosioka I, Matsuda A, Kitagawa I (1966a) Pyxinic acid, a novel lichen triterpene with 3p-hydroxyl function. Tetrahedron Lett 613-616... 

In addition to the previously described pyxinic acid (485) 339), Yosioka et al. 345) have isolated methyl pyxinate (486) and methyl 3-0-acetylpyxinate (487) from Pyxine endochrysina. The structure of these esters was verified by direct comparison with the synthetic derivatives obtained from pyxinic acid. 

Yosioka, I., A. Matsuda, and I. Kitagawa Pyxinic Acid, a Novel Lichen Triterpene with 3p-Hydroxyl Function. Tetrahedron Letters 1966, 613. 

Two new hopanes, methyl pyxinate (172) and the corresponding acetate (173), occurin the lichen Pyxine endochrysina along with several dammaranes. Full papers have appeared on the structure of leucotylic acid (174) and on the correlation of zeorin (175) with leucotylin (176). On treatment with acid, methyl leucotylate (177) and leucotylin (176) afford methyl isoleucotylate (178) and isoleucotylin (179), respectively. 

Deriv Triacetylpyxinol, needles (MeOH-HjO), mp 180-181 °C, from pyxinol with ACjO-tolu-ene-p-sulphonic acid at 28 °C in 20 h StL Pyxine endochrysina Nyl. 

Leucotylic acid (98), phlebic acid A (99), and phlebic acid B (100) are hopane derivatives with a 23-carboxylic acid from Parmelia leucotyliza yl., P. entotheiochroa Hue, and Peltigera aphthosa (L.) Willd. Diacetyl pyxinol (101), known from Pyxine endochrysina yX., possesses adammaran skeleton from X-ray analysis of 3/3, 12/3-di-/ -bromobenzoyl pyxinol. 

In 1965 Chandrasenan et al. (65) proposed structure 514 for pyxiferin, the main pigment from Pyxine coccifera. This substance was subsequently synthesized (see Scheme 159) and found to differ from natural pyxiferin. Later on Huneck (380) identified pyxiferin with chiodectonic acid and proposed structure 515 for this pigment. 

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