Germacrane lactone

The isolation and identification of germacrane lactones from a host of plant sources is an area of continuing interest particularly in the laboratories of Professors Herz and Bohlmann. The search for biologically active compounds and the chemotaxonomic classification of plant species are the two major driving forces for this research. The sub-division of these lactones into germacranolides (479)—... 

Synthesis of germacrane sesquiterpenoid lactones and related compounds 99T2115. 

Epoxy-5,10-dihydoxy-6a-angeloyloxy-9 (3-isobutyloxy germacran-8a, 12-olide (germacranolide sesquiterpene lactone) Carpesium divaricatum (Asteraceae) l iNOS expression [per inhibiting NFkB activation]... 

Reduction of the photo-adduct (446) derived from (+)-isopiperitone and cyclobutene-1-carboxylic acid with NaCNBH3 gives the lactone (447). Thermolysis of this compound affords the 6a-epimer of isoaristolactone (448) and the elemanolide (449).213 A novel approach to the synthesis of germacranes involves the thermal opening of a bridgehead cyclobutene which, in turn, is derived by an oxy-Cope rearrangement (Scheme 57).214... 

Cardui benedicti herba Cnici herba Blessed thistle Cnicus beiiedictus L. Asteraceae DAC 86. GAB 90, MD Sesquiterpene lactons (-0.25%), (germacran type) cnicin, salonitenolid and artemisiifoliii lit of the drug, 800-1800 Essential oil (0.03%-0.1%) citral, cilronellal cinnamic acid, acetylene derivatives Pig. 8... 

Fig. (1). Major sesquiterpenoid skeletal types representing the structural basis for 87% of all STLs [4]. The numbers indicate the number of lactones, those in brackets the total number of entries in each of the classes (VS1600-VS2470). Common modes of lactonization as found among all these types are shown for the germacrane type. (Note that C-6 and C-8 are actually equivalent in this further unsubstituted representation of the germacrane skeleton which, however, does not occur in nature).

GermacranoBdes. Bicyclic sesquiterpene lactones derived from the germacranes. The lactone ring is usually in the 7/3,8a-position as in pyrethrosin it can also be in the 7, 6a-position but is only rarely seen in the 4,6-position as in linderalactone. 

The Cope rearrangement has featured in two recent germacrane syntheses. Dehy-drosaussurea lactone (139) has been shown to be converted directly into costunolide... 

StilP has provided an expeditious route to germacranes such as ( )-acorager-macrane (19), based on an oxy-Cope rearrangement. The planning of syntheses of vernolepin and related sesquiterpene lactones has been discussed in full papers, and syntheses of insect sex attractants have been reviewed. ... 

Germacranes with trans,trans 1,5-diene system are thermally labile and undergo Cope rearrangement to give products with elemane skeleton. Thus, costunolide (195) on heating gives saussurea lactone (205), albeit, in low yield. 

Plants of the family Asteraceae, which are used as a spice and for the production of bitter liqueurs and vermouths (aroma-tised fortified wine flavoured with various botanicals), contain sesquiterpenic lactones derived from guaiane (8-226), eudesmane (8-250) and germacrane (8-251). Eudesmane (also known as selinene) has the systematic name (JS,4aJ ,7 R,8aS)-7-isopropyl-l,4a-dimethyldecahydronaphthalene, germacrane is (lJ ,4S,7S)-4-isopropyl-l,7-dimethylcyclodecane. 

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