ChemInform Abstract: Boron Analogues of Choline. Part 2. Efficient Syntheses of Boron Analogues of Choline, Acetylcholine, and Substituted Acetylcholines.
Abstract
An efficient synthesis of isoelectronic and isostructural boron analogues (IIIa)-(IIId) of choline and acylcholines from the reaction of the corresponding ester hydrochlorides (II) with Et4NBH4 is described.
ChemInform Abstract
An efficient synthesis of isoelectronic and isostructural boron analogues (IIIa)-(IIId) of choline and acylcholines from the reaction of the corresponding ester hydrochlorides (II) with Et4NBH4 is described. The ester hydrochlorides (II) are prepared from the ethanolamine (I) and HCl or acyl chlorides. (I) reacts with phenoxyacetyl chloride to give the alcohol hydrochloride (IIa) and the ester (IVc) (yield 45%) which adds BH3 to afford (IIIe). (IIIb) is obtained with 59% yield similarly from (IVc), the byproduct from the reaction of (IIb) with NEt4BH4. Cocondensation of trimethylamine-carboxyborane and the B analogue of choline (IIIa) in the presence of dicyclohexylcarbodiimide produces the (trimethylamineboryl-carbonyl)choline (V). The B analogues (VIII) of suberoyldicholine is prepared from the reaction of the corresponding diester hydrochloride (VII) as shown.
