Aldimines are conveniently metallated, at a position α to the functional group, by using very powerful bases i.e. activated lithium dialkylamides generated in situ from lithium and a secondary amine in benzene/hexamethylphosphoric triamide. The anions obtained are alkylated with various ω,ω′-dihalogenoalkanes to give, after aqueous acid hydrolysis, good yields of ω-halogenated aldehydes and dialdehydes
7-Bromo-beta-carboline compound and method for producing same
申请人:Kawaken Fine Chemicals Co., Ltd.
公开号:EP0273321A1
公开(公告)日:1988-07-06
A 7-bromo-β-carboline compound of the formula (I):
wherein R¹ - H or C₁ - C₅ alkyl and R² = C₁ - C₅ alkyl or benzyl, is produced by reacting a β-carboline compound of the formula (II):
wherein R¹ and R² are as defined above and R³ = H, C₁ - C₅ alkyl, C₁ - C₅ alkoxy or benzyloxy, with a brominating agent in an organic solvent in the presence of an alkalic and then hydrolyzing the resultant procursory 7-bromo-β-carboline compound of the formula (III):
in a solvent in the presence of a mineral acid.
AbstractNatural Vincamine (1) has been synthesized in an enantioselective manner starting from the ethylpentenal7. In the key step a mixture of the diastereoisomeric racemates,14and15, was directly obtained from the silyl enol ether11and the dihydro‐β‐carboline12by the way of an intramolecularMannichreaction of the intermediate13(Scheme 4). The undesired stereoisomers,14and15b, were recycled to15ausing the related reversibleMannichreaction18 ⇄ 14 + 15, followed by crystallization of the salt from15aand (+)malic acid.15awas converted to natural vincamine (1) in several steps including the known transformation20→1.
Method for producing a 5-bromo-1-pentanal compound or an acetal derivative thereof