Synthesis of Laurencione, a Labile Dihydro-3(2H)-furanone Derivative from the Red Alga Laurencia spectabilis
摘要:
The first total synthesis of laurencione, a naturally occurring dihydro-3(2H-furanone derivative isolated from the red alga Laurencia spectabilis, is described. The synthesis is comprised (1) of conversion of gamma-butyrolactone into alpha,alpha-dimethoxy-gamma-butyrolactone, (2) addition of methyllithium across the lactone carbonyl, and (3) acid hydrolysis of the acetal moiety. An alternative synthesis consists of the acid-catalyzed conversion of 3,3-dimethoxy-2-hydroxy-2-methyltetrahydrofuran into laurencione methyl ether and subsequent acid-catalyzed hydrolysis. In addition, a convenient synthesis of the coffee and caramel flavor component 2-methyl-3(2H)-furanone has been developed by acid-catalyzed rearrangement of 2-methoxy-2-methyltetrahydrofuran-3-one.
New Methods for Stereoselective Synthesis of α-Alkylidene-γ-butyrolactones Using Monoanion of<i>O</i>-Ethyl<i>S</i>-(Tetrahydro-2-oxo-3-furanyl) Thiocarbonate and Dianion of α-Mercapto-γ-butyrolactone
The lithium enolates of O-ethyl S-(tetrahydro-2-oxo-3-furanyl) dithiocarbonate and thiocarbonate were found to be efficient reagents for the stereoselective synthesis of α-alkylidene-γ-butyrolactones fromcarbonylcompounds. The dianion of α-mercapto-γ-butyrolactone was successfully generated by treatment of α-mercapto-γ-butyrolactone with 2.2 equivalents of lithium diisopropylamide in the presence
1-(Indolyl-3-alkyl)-3 or 4-(ureido or guanidino)-piperidines, e.g. those of the formula ##STR1## acyl derivatives and salts thereof are antihypertensive agents.
Hypotensive indolylalkylpiperidyl guanidines and isoureas
申请人:Ciba-Geigy Corporation
公开号:US04242347A1
公开(公告)日:1980-12-30
1-(Indolyl-3-alkyl)-3 or 4-(ureido or guanidino)-piperidines, e.g. those of the formula ##STR1## R=H; alkyl; free, etherified or esterified OH or SH; CF.sub.3, NO.sub.2 or NH.sub.2 m=1-4; n=2 or 3; X=O, S or NH acyl derivatives and salts thereof are antihypertensive agents.
1-(Indolyl-3-alkyl)-3 or 4-(ureido or guanidino)-piperidines, e.g. those of the formula ##STR1## R= H; alkyl; free, etherified or esterified OH or SH; CF.sub.3, NO.sub.2 or NH.sub.2 m= 1-4; n= 2 or 3; X= O, S or NH acyl derivatives and salts thereof are antihypertensive agents.