Stereoselective synthesis of enantiomerically pure inherently chiral p-tert-butylcalix[4]arene carboxylic acids

Both enantiomers of inherently chiral dipropoxy-p-tert-butylcalix[4]arene carboxylic acids with AABH substitution patterns have been prepared by the stereoselective reactions of 25,26-dipropoxy-p-tert-butylcalix[4]arene with enantiomerically pure (S)- or (R)-N-(1-phenylethyl)bromoacetamide, separation of the diastereomers by recrystallization, and removal of the chiral auxiliary groups. The absolute configurations of the obtained compounds have been established by X-ray analysis.

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(cS)-5,11,17,23-Tetra-p-tert-butyl-27,28-dipropoxy-25-hydroxy-26-(S)-N-(1′-phenylethyl)aminocarbonylmethoxycalix[4]areneС60Н79NО5[α]D20=-6.3 (c 0.015 M, CHCl3)Source of chirality: inherently chirality, chiral carbonAbsolute configuration: (cS), (S)

(cS)-5,11,17,23-Tetra-p-tert-butyl-27,28-dipropoxy-25-hydroxy-26-(R)-N-(1′-phenylethyl)aminocarbonylmethoxycalix[4]areneС60Н79NО5[α]D20=+9.5 (c 0.015 M, CHCl3)Source of chirality: inherently chirality, chiral carbonAbsolute configuration: (cS), (R)

(cS)-5,11,17,23-Tetra-p-tert-butyl-27,28-dipropoxy-25-hydroxy-26-carboxymethoxycalix[4]areneС52Н70О6[α]D20=-14.1 (c 0.016 M, CHCl3)Source of chirality: inherently chiralityAbsolute configuration: (cS)

(cS)-5,11,17,23-Tetra-p-tert-butyl-26,27-dipropoxy-25-hydroxy-28-methoxycarbonylmethoxycalix[4]areneС53Н72О6[α]D20=-7.5 (c 0.016 M, CHCl3)Source of chirality: inherently chiralityAbsolute configuration: (cS)