Syntheses of S-Enantiomers of Hanishin, Longamide B, and Longamide B Methyl Ester from l-Aspartic Acid β-Methyl Ester: Establishment of Absolute Stereochemistry

Abstract

[reaction: see text] Total syntheses of enantiopure hanishin, longamide B, and longamide B methyl ester are described. Absolute configurations of these natural products have been established.

One-Pot Conversion of Carbohydrates into Pyrrole-2-carbaldehydes as Sustainable Platform Chemicals

“…To a solution of the above pyrrole carboxylic acid in dry DMF (5 mL) were added K 2 CO 3 (0.88 g, 6.4 mmol) and CH 3 I (1.14 g, 8.0 mmol). (-)-Hanishin (11): 19,22,25 To a stirred solution of azido methyl ester 17 (0.30 g, 1.07 mmol) in dry MeOH (20 mL) was added activated 10% Pd on carbon (0.053 g, 0.05 mmol Pd). The mixture was stirred under 1 atm pressure of H 2 gas for 2 h. The mixture was then filtered through a short pad of celite and solvent was evaporated under reduced pressure.…”

“…The azide reduction by catalytic hydrogenation, intramolecular amidation in refluxing toluene, and the known bromination using NBS (2.0 equiv.) 22,24 finally produced (-)-Hanishin 11 in 69% yield (23% overall yield from D-ribose). We developed a practical one-pot conversion method of carbohydrates and primary amines with a stoichiometric oxalic acid in DMSO at 90 ºC for 30 min, in which N-substituted pyrrole-2-carbaldehydes 4 were obtained in 21~53% yields.…”

Biosynthesis, asymmetric synthesis, and pharmacology, including cellular targets, of the pyrrole-2-aminoimidazole marine alkaloids

“…Following two racemic syntheses, the absolute configuration of natural cyclooroidin was confirmed by asymmetric synthesis in 2006 by Pelloux-Leon and Minassian, 65 expanding on their previous synthesis of the longamide B ( 89 ) related from ( L )-aspartic acid methyl ester ( 90 , Scheme 18). 66 After conversion of the carboxylate moiety of longamide B ( 89 ) into the corresponding mixed anhydride, sequential treatment with diazomethane and aqueous hydrogen bromide delivered the optically active bromoketone 93 . Subsequent reaction with Boc-guanidine directly generated the aminoimidazole ring, and cleavage of the carbamate protecting group delivered cyclooroidin ( 32 ).…”

From anti-fouling to biofilm inhibition: New cytotoxic secondary metabolites from two Indonesian Agelas sponges

“…Whereas, (S)-(À)-longamide B methyl ester was later synthetically produced. 48 Longamide B methyl ester has two bromine atoms. 47 However, the molecular weight of 18 is 64 mass units greater than that of longamide B methyl ester.…”