Manumycin A:  Synthesis of the (+)-Enantiomer and Revision of Stereochemical Assignment

Highly Enantioselective Epoxidation of 2‐Methylnaphthoquinone (Vitamin K3) Mediated by New Cinchona Alkaloid Phase‐Transfer Catalysts

“…M.p. 1-N-(9-Anthrylmethyl)-9-O-benzyl-6'-hydroxycinchonidinium chloride (17): By following the general procedure for the quaternisation of tertiary amines, 17 was obtained from 9-O-benzyl-6'-hydroxychinchonidine (18) [23] (1.00 g, 2.50 mmol) using work-up B as a yellow solid (713 mg, (20): A 250 mL round-bottomed flask with argon inlet was charged with alcohol 42 (1.55 g, 6.45 mmol, 1.00 equiv) and dry toluene (70 mL). The mixture was cooled to 0 8C and PCl 5 (2.70 g, 12.9 mmol, 2.00 equiv) was added.…”

“…[17][18][19] Oxiranes of the latter type are valuable building blocks for pharmaceutical and natural products. 2-Methyl-1,4-naphthoquinone (vitamin K 3 (7), Scheme 2) has often served as the touchstone for catalyst performance, because it is a particularly challenging substrate with respect to enantioselective epoxidation.…”

Enantioselective Organocatalysis

“…[159] This reaction was used in the synthesis of different members of the manumycin family (Scheme 42). [160] The use of one equivalent of N-benzylchinidinium chloride 47 a (R H; X Cl), and tert-butyl hydroperoxide (TBHP) with a catalytic amount of sodium hydroxide gave the desired epoxide with 89 % ee (Scheme 42). The reaction conditions were also optimized for the oxidation of some chalcone derivatives.…”

Diastereoselective Spiroannulation of Phenolic Substrates: Advances Towards the Asymmetric Formation of the Manumycin m-C7N Core Skeleton

“…While there are already numerous syntheses of members of the Manumycins [5][6][7][8][9][10][11][12][13], Aranorosins [14][15][16] and Gymnastatins [17], this new approach could be advantageous since it may allow for the synthesis of more than one of these structures from the same starting material. We have investigated the asymmetric synthesis of spirolactones 5 ( Figure 2) bearing substituents that would mimic the general functionality found in most members of the Manumycin family (cf.…”