Absolute configuration of glycerol derivatives. 7. Enantiomers of 2-[[[2-(2,6-dimethoxyphenoxy)ethyl]amino]methyl]-1,4-benzodioxane (WB-4101), a potent competitive alpha-adrenergic antagonist.

The enantiomers of 2-[[[2-(2,6-dimethoxyphenoxy)ethyl]amino]methyl]-1,4-benzodioxane (4) were prepared from the chiral 2-[(tosyloxy)methyl]-1,4-benzodioxanes [(2S)- and (2R)-5]. The corresponding (2R)- and (2S)-2-(aminoethyl)-1,4-benzodioxanes [2R)- and (2S)-7] were prepared by a modified Gabriel synthesis and converted to the enantiomers of 4 by condensation with 2,6-dimethoxyphenoxyacetaldehyde (8) and reduction of the intermediate imine with NaBH4. The enantiomer (2S)-4 was 40--50 times as potent as the enantiomer (2R)-4 in antagonizing the alpha-adrenergic response of methoxamine-induced contraction of rabbit aortic strips, showing a pA2 = 9.0. This result is consistent with the previous observation that S enantiomers of 2-[(alkylamino)methyl]benzodioxanes are more potent antagonists at a alpha-adrenergic receptors than the R enantiomers.