ISSN:
0018-019X
Keywords:
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Leaf-gland Pigments: 3β-Acetoxyfuerstione, Nilgherron A and Nilgherron B, New Quinomethanes from Plectranthus nilgherricus BENTH. (Labiatae); Absolute Configuration of FuerstioneWe have isolated from leaf-glands of the above mentioned plant the following deeply coloured quino-methane derivatives: (1) traces of the already known fuerstione (1a); 11,15-dihydroxy-5,7,9 (11), 13-abietatetraen-12-one; (2) the new 3β-acetoxy-fuerstione (1b); (3) nilgherron A (5a, I or II), a new dimeric diterpenoid quinomethane, C40H52O7, formed in the plant obviously by cycloaddition of the o-quinone 8 (9aS, 11R)-11 -hydroxy-2-(1-hydroxy-1-methylethyl-9,9-dimethyl-3,4,7,8,9,9a,10,11- octahydro-5H-dibenzo [a, d]cycloheptene-3,4-dione) with fuerstione; (4) nilgherron B (5b, I or II), C42H54O9, likewise a new compound, formed by the same type of cycloaddition (heterodiene synthesis) of 8 with 3β-acetoxyfuerstione. On the basis of 1H-NMR. shift arguments structure I is slightly preferred to II for 5a and 5b. Model experiments have shown the easy formation of the dihydrodioxin ring by reaction of an o-benzoquinone with p-quinomethanes. The absolute configuration of fuerstione and 3β-acetoxyfuerstione has been determined by chiroptical methods.
Additional Material:
1 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/hlca.19770600832
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