Labda-8

Di88 Labda-8( 17), 13-dien-15,12R -olid-19-oic acid T. standishii EBV [125]... 

The Chemistry of the Tetracyclic Diterpenoids.—The reaction of cnt-kaur-16-ene with thallium(lli) nitrate affords cnt-kaur-16-en-15j8-ol nitrate which undergoes a ready [3,3] sigmatropic rearrangement to cnt-kaur-15-en-17-ol nitrate. The reactions of phyllocladene and of labda-8(17)-en-13-ol with sodium azide and iodine chloride have been examined. ° The synthesis of 13-hydroxylated cnt-kaur-16-ene derivatives such as steviol using an acyloin-like cyclization of keto-esters has been developed. A detailed analysis was made of the products arising from the use of sodium in liquid ammonia in this reaction. 

Achilladelis and Hanson have studied the incorporation of [2- C,2- H2]-, [2- C,3J ,4R- H]-, and [2- C,5- H2]-mevalonic acid into rosane terpenoids (60). Their results, together with the non-incorporation of pimaradiene, excludes any diene intermediates between (59) and (60). Since labda-8(17),13-diene-15,19-diol... 

From the petroleum ether extract of the rhizomes of A. speciosa, dihydro-5,6-dehydrokawain (66) and 5,6-dehydrokawain (67) were isolated both compounds were also found in the rhizomes of A. kumatake [53]. From the leaves of 4. speciosa, dihydro-5,6-dehydrokawain (66) and compound 68 were isolated and identified and 66 was found to be plant growth inhibitor [54]. Several derivatives related to 66 were synthesized and evaluated for their phytotoxic effects and compound 69 was found to be the most effective [54]. The petrol-soluble fraction of the aqueous methanolic extract of the fresh rhizomes of A. speciosa yielded methyl tranj -cinnamate, alpinetin, cardamonin, flavokawin B (70) and dihydroflavokawin B (71) as well as 66 and 67 [52]. Two diterpenes were also isolated from the petrol-soluble fraction of the same rhizomes and elucidated as labda-8(17),12-diene-17,16-dial (11) and ( )-15,16-bisnorlabda-8(17),l l-dien-13-one (72) [55]. Alpinetin and cardamonin were isolated from the seeds of A. speciosa from India [56]. Terpenoids of the essential oil obtained from the leaves of A. speciosa from Brazil were analyzed by GC-MS [57]. 

Labda-8( 17), 12-diene-15,16-dial and coronarin E were isolated from the chloroform extract of the rhizomes of A. javanica [58]. The distribution of these two labdane diterpenes within the Zingiberaceae was reported [58]. 

A new labdane diterpene, ( )-labda-8(l 7), 12-diene-15-ol-16-al (84) was isolated from the rhizomes of A. formosana together with ( )-15,16-bisnorlabda-8(17),l l-diene-13-one, two known sesquiterpenes, furopelargone B and humulene epoxide, and three known phenolic compounds, methyl traws-cinnamate, dihydro-5,6-dehydrokawain and dihydroflavokawin B [62]. The chemotaxonomic significance of these compounds was discussed briefly [62]. 

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