Tetrahydrofuran → (3aR,6aS)-2-Hydroxy-3,3a,6,6a-tetrahydro-2H-cyclopenta[b]furan-5-carbaldehyde

Reaktionsgleichung

C(=O)[CH2:2][CH2:3][CH:4]=[O:5].N1[CH2:14][CH2:13][CH2:12][C@H:8]1[C:9]([OH:11])=[O:10].C1COCC1>CC1OCCC1>[OH:10][CH:9]1[O:11][C@H:13]2[CH2:14][C:3]([CH:4]=[O:5])=[CH:2][C@H:12]2[CH2:8]1

Komponenten

Versuchsvorschrift

The solution of succinaldehyde 8 from the first step (109.5 g, 1.272 mol) in 2-MeTHF was stirred at r.t. (S)-Proline (2.93 g, 25.4 mmol, 0.02 eq.) was added as a solid and the reaction stirred at r.t. for 20 h. THF (650 ml) was added, followed by [Bn2NH2][OCOCF3] (8.43 g, 25.4 mmol, 0.02 eq.). The reaction was stirred for a further 14 h. Celite (60 g) was added to the reaction and the volume of the reaction mixture was reduced by ¾ under reduced pressure. tert-Butyl methyl ether (TBME) (an equal volume to the volume of THF/2-MeTHF removed) was added slowly (over ˜15 mins) and with vigorous stirring of the mixture. The mixture was stirred for 20 min before filtration of the resulting solids (through a sinter funnel). The solids were washed with TBME (3×150 ml) and the filtrate was concentrated under reduced pressure. The material was purified by column chromatography (˜600 g silica), eluting with petrol/EtOAc (6:4 to 5:5), to give the lactol 7 (as an approximately 2:1 mixture of diastereoisomers), as a brown oil.