Reaction #50741

Reaction equation

L-Selectride

lithium tri-sec-butylborohydride

methanol

(-)-narwedine

→

(-)-galanthamine

Yield 99.5%

Solvents

THF

CHCl3

THF

Conditions

Workup

1. 1
   workup.ADDITIONAfter addition
2. 2
   Temperaturewarmed to 0° C
3. 3
   Temperaturethe solution is warmed to 25° C.
4. 4
   workup.STIRRINGstirred for 15 minutes
5. 5
   OtherSolvent is then evaporated under vacuum to dryness
6. 6
   Otherto obtain a syrup
7. 7
   WashThe column is eluted with a solvent mixture of CH2Cl2 /CH3OH 6:1

Procedure

2 mmole (1 N in tetrahydrofuran {THF}) of L-Selectride® (lithium tri-sec-butylborohydride, Aldrich)is charged into 8 ml THF and cooled to -78° C. 1 mmole of (-)-narwedine in 50 ml THF is added dropwise over a period of 30 minutes. After addition, the solution is stirred at -78° C. for 2 hours and then warmed to 0° C. 0.4 ml of methanol is added and the solution is warmed to 25° C. and stirred for 15 minutes. Solvent is then evaporated under vacuum to dryness to obtain a syrup. The syrup is dissolved in 0.5 ml CHCl3 and the solution is loaded into a SiO2 200-400 mesh, 6A, column. The column is eluted with a solvent mixture of CH2Cl2 /CH3OH 6:1 to obtain 286 mg of pure (-)-galanthamine (a yield of 99.5%). HPLC of the resultant mixture indicates there is no epigalanthamine or lycoramine present. {m.p. 128°-129° C.; [α]D25 =-93.4}. Natural (-)-galanthamine has a melting point of 126°-127° C. ([α]D25 =-91.0)

Source