Isolation and structure of two diterpene quinones from Salvia Ballotaeflora Benth (Labiatae)

Collective Syntheses of Icetexane Natural Products Based on Biogenetic Hypotheses

“…[17,19] In this regard, the dried ethanolice xtract of rosemary was dissolved in Et 2 Oa nd extracted with NaOH (1 m)t of ormt he aqueous soluble sodium salts of different phenols (Scheme 4). [12,13] The attack of water on such acarbocation was suggested to be disfavored from the b facea ccording to Dreiding models, therefore supporting an enzymatically guided attack. HCl) and ethereal extraction of the aqueous phase yielded ap henolic abietaneenriched extract, which was subjected to exhaustive methylation (NaH, Me 2 SO 4 ,T HF,t hen MeOH)t oy ield am ixture of the desired trimethylated carnosic acid 8 and byproducts.…”

“…[20] Indeed, the sterically less congested 11-methoxy group was selectivelyd emethylatedw ith complete regioselectivity in high yield (80 %) to result in the first synthesis of salvicanol (12). [20] Indeed, the sterically less congested 11-methoxy group was selectivelyd emethylatedw ith complete regioselectivity in high yield (80 %) to result in the first synthesis of salvicanol (12).…”

“…[20] Indeed, the sterically less congested 11-methoxy group was selectivelyd emethylatedw ith complete regioselectivity in high yield (80 %) to result in the first synthesis of salvicanol (12). [23] Salvicanol (12)w as acetylated in high yield (90 %) to afford salvicanol acetate (13), whichw as used later on for the subsequentoxidationr eaction. [21] The alkenes 10,o btained in the course of the ring expansion of 9,w erec onverted into salvicanol (12)i n two consecutive steps consisting of an epoxidation carriedo ut by using m-chloroperoxybenzoic acid (m-CPBA) [22] and aw ell- established one-poth ydride (l-selectride)-mediated epoxide opening/demethylation in ay ield of 42 %o ver the two steps.…”

“…The successfulf ormation of 17 in the presence of TBHP encouraged us to investigate differentc ombinations of transition-metal catalysts and TBHP (entries [5][6][7][8][9][10][11][12]. Indeed, the formationo ft he desired product 17 was observed by utilizing severalt ransition metals (entries 6-9, 11,a nd 12).…”

Synthetic studies on the icetexones: enantioselective formal syntheses of icetexone and epi-icetexone

“…Icetexone ( 1 ) was the first compound in this family to be isolated and characterized from the aerial parts of Salvia ballotaeflora Benth in 1976 along with the ortho -quinone tautomer, romulogarzone ( 3 ). 2 X-ray crystallographic analysis enabled a determination of the absolute configuration of 1 , the name of which has been used to represent this family of natural products. 3 Other members of the icetexone subclass, such as 7,20-dihydroanastomosine ( 4 ), 19-deoxyisoicetexone ( 5 ), and 19-deoxyicetexone ( 6 ) have subsequently been isolated from the same source.…”