Studies on the sesquiterpene lactones from Laurus novocanariensis lead to the clarification of the structures of 1-epi-tatridin B and its epimer tatridin B.

The germacranolide 1-epi-tatridin B has been isolated from the aerial parts of Laurus novocanariensis. We have observed that the identification of this lactone and its epimer tetradin B in the scientific literature is confusing and contradictory. We have therefore studied this issue clarifying errors and contributing to the structural elucidation of other related products. Moreover, we have isolated from this plant a lactone with an 1,5-ether bridge, previously obtained from Austrolabium candidum. We have now named it austroliolide, reassigned its 13C NMR spectrum and compared its structure with that of badgerin. In addition, we have also isolated from L. novocanariensis the known germacranolides artemorin, costunolide, tatridin A, tulirinol and verlotorin, the eudesmanolides ß-cyclopyrethrosin, 1ß-hydroxy-arbusculin A, magnoliaolide and reynosin, and the guaianolide dehydrocostus lactone.

The Dimerization of Precocene I.

In an earlier work we reported that treatment of precocene I with Brönsted and Lewis acids produces its oligomerization, giving dimers, trimers, tetramers, etc. Now, in this article we show that bromination of precocene I with phenyltrimethylammonium tribromide (PTT) blocks its oligomerization giving a dibromo- dimer, which was reduced with tri-n-butyl tin hydride affording the same dimer obtained in the reactions with acid, thus avoiding the oligomerization. Additionally, the oxidations of precocene I with Jones reagent afforded the corresponding 3-hydroxy-4-chromanone, 3,4-chromandione, 3,4-diacid, and two dimers.

On the structures of the diterpenes licamichauxiioic acids A and B.

The structures of the diterpenes licamichauxiioic acids A and B, isolated from Licania michauxii, which had been reported as 15-oxo-ent-kaur-9(11),16-dien-19-oic acid (1) and 15-oxo-ent-kaur-13,16-dien-19-oic acid (3), respectively, are not correct. Starting from grandiflorenic acid (6) we had prepared a compound with the proposed structure for licamichauxiioic acid A, and its spectroscopic data are different from those given for this acid. In the case of licamichauxiioic acid B, its NMR data are not in accordance with the proposed structure 3, which also violates Bredt's rule. In addition, we described a useful method for the separation of grandiflorenic and grandiflorolic acids.