Diastereomeric process-based chiral resolution of helical quinone derivatives using (−)-menthyl chloroformate

Synthesis of Enantiomerically Pure Oxa[9]helicene Derivatives by a Nucleophilic Cyclodehydration Reaction of Helical 1,1′-Bibenzo[c]phenanthrenylidene-2,2′-dione

“…sequent hydrolysis of the diastereomers followed by oxidation gave the respective isomers of quinone derivatives 1 with enantiopurities exceeding 99.5% (Scheme 1). 10,11 We therefore hoped that enantiopure oxa [9]helicene derivatives might be obtained by the reaction of enantiopure 2,2′-diphenoquinones 1 with various nucleophiles. Starting from the enantiopure starting substrates 1, we undertook a stereospecific synthesis of enantiomerically pure functionalized oxa [9]helicene derivatives and studied their stereochemistry.…”

“…Enantiomerically pure (>99.5% ee) quinones 1 were obtained by using the aforementioned diastereomeric separation method. 11 Four different conditions were used to synthesize enantiomerically pure oxa [9]helicene derivatives 2 and 3, according to previously reported methods. [6][7][8][9] The assynthesized compounds were purified by using a normalphase (LiChrosorb Si-60) column and characterized by 1 H NMR, 13 C NMR, and mass spectroscopy.…”

“…Subsequent hydrolysis of the diastereomers followed by oxidation gave the respective isomers of quinone derivatives 1 with enantiopurities exceeding 99.5% (Scheme 1 ). 10 11…”

Helical Amide Derivatives: Synthesis by Insertion of Aliphatic ­Primary Amines into Benzo-Fused 2,2′-Diphenoquinones and Dia­stereomeric Resolution

“…For example, 1b-d reacted with n-propylamine at a slightly increased temperature of 40 °C. These eactions took a longer time, such as, 4 to 5 days to complete, resulting in comparatively low yields (entries [10][11][12]. Furthermore, when the starting helical quinone 1a reacted with an optically active aliphatic primary amine, such as (R)-(+)-1-phenylethylamine, a mixture of two diastereoisomers (P,R)-2ag and (M,R)-2ag, was obtained.…”

“…We previously reported a diastereomeric resolution method for racemic quinone 1a, in which the mixture was separated by HPLC, and subsequent hydrolysis followed by oxidation gave the corresponding isomers of the quinone derivatives (P)-1a and (M)-1a with enantiopurities exceeding 99.5%. 10,11 When enantiomerically pure helical quinones (P)-1a and (M)-1a reacted with propylamine in CHCl 3 at room temperature, (P)-2aa and (M)-2aa were obtained as the major products in yields of 66 and 64%, respectively. A positive specific rotation was observed for (P)-2aa {[] D 25 = +1236 (c 1.05 × 10 -2 , MeCN)}, whereas a negative specific rotation was observed for (M)-2aa {[] D 25 = -1130 (c 1.05 × 10 -2 , MeCN)} (Table 3, entries 1 and 2).…”