An Enantiodivergent Synthesis of (+)‐ and (−)‐Centrolobines by Asymmetric Esterification Catalyzed by (R)‐(+)‐N‐Methylbenzoguanidine ((R)‐NMBG)

Silylative Kinetic Resolution of Racemic 1-Indanol Derivatives Catalyzed by Chiral Guanidine

“…In our research group, chiral guanidine-based catalyst ( R )- N -methylbenzoguanidine (( R )-NMBG 1 ) was found to facilitate efficient acyl transfer for the kinetic resolution of racemic benzylic alcohols via asymmetric esterification in the presence of pivalic anhydride . To demonstrate an application of this protocol, we achieved an enantiodivergent synthesis of both enantiomers of centrolobine using the developed catalyst in the synthetic key step . Furthermore, we recently reported the acylative kinetic resolution of racemic aromatic β-hydroxy esters with cyclohexanecarboxylic anhydride in the presence of ( R )-NMBG 1 and its derivative ( R,R )- N -(1-(β-naphthyl)­ethyl)­benzoguanidine (( R,R )-NβNpEtBG 2 ) .…”

“…With the optimized reaction conditions in hand, we attempted to further improve selectivity. Thus, three further guanidine catalysts, ( R,S )-NPhEtBG 6 , ( R,R )-NPhEtBG 7 , and ( R,R )-NβNpEtBG 2 (previously reported by our research group in application to acylative kinetic resolution), were applied to the silylative kinetic resolution of (±)- 3 (Table ). Comparison of the performance of diastereomeric catalysts ( R,S )-NPhEtBG 6 and ( R,R )-NPhEtBG 7 revealed that the ( R,R )-configuration led to better results (entries 2 and 3, respectively).…”

Acylative Kinetic Resolution of Racemic 2,2‐Dimethyl‐Substituted Nitroaldol (Henry) Adducts Using a Chiral Guanidine Catalyst: (R)‐(+)‐N‐Methylbenzoguanidine ((R)‐NMBG)

“…In our research group, a chiral guanidine‐type catalyst, ( R )‐ N ‐methylbenzoguanidine [( R )‐NMBG ( 1 )], was synthesized and applied in the kinetic resolution of racemic benzylic alcohols with carboxylic acids using pivalic anhydride via a dehydrative condensation reaction . Furthermore, we achieved an efficient enantiodivergent synthesis of both enantiomers of centrolobine using this reaction as the key step . We recently revealed that ( R )‐NMBG ( 1 ) and its derivative ( R,R )‐ N ‐[1‐(β‐naphthyl)ethyl]benzoguanidine [( R,R )‐NβNpEtBG ( 2 )] can serve as efficient acyl transfer catalysts for the acylative kinetic resolution of racemic aromatic β‐hydroxy esters (±)‐ 3 using cyclohexanecarboxylic anhydride (Scheme (a)) .…”

Lipase-Catalyzed Resolution of 1-[4-(Benzyloxy)phenyl]hex-5-en-3-ol: Synthesis of (-)-Centrolobine

“…Owing to excellent biological activities and its simple chemical structure, many research groups have been paid attention for its synthesis in racemic form [15][16][17][18][19] as well as in enantiomerically form [14,[20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38].…”