Mono-etherification of racemic propane-1,2-diol by a tin(II) bromide catalyzed reaction with diazofluorene and a study of the Pseudomonas cepacia lipase catalyzed acetylation of the mono-ethers

The tin(II) bromide catalyzed reaction of diazofluorene with racemic propane-1,2-diol in 1,2-dimethoxymethane gave the 1- and 2-monoethers in similar amounts. After tritylation of the 2-ether, 2-(9H-fluoren-9-yloxy)-1-triphenylmethyloxypropane and 1-(9H-fluoren-9-yloxy)propan-2-ol were obtained in pure form. The enantiomeric 1-fluorenyl ethers were resolved by kinetic resolution by transacetylation with the help of Pseudomonas cepacia lipase and both enantiomers of the propane-1,2-diol were obtained after deprotection. The racemic 2-(9H-fluoren-9-yloxy)propan-1-ol was obtained after de-triphenylmethylation. However, transacetylation onto this alcohol under identical conditions to those used for the 1-fluorenyl ether showed no enantioselectivity.

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(R)-1-(9H-Fluoren-9-yloxy)propan-2-yl acetateC18H18O3[α]D20=+22.4 (c 1.32, CHCl3)Source of chirality: enzymatic resolutionAbsolute configuration: (R)

(R)-1-(9H-Fluoren-9-yloxy)propan-2-olC16H16O2[α]D20=+2.8 (c 1.17, CHCl3)Source of chirality: enzymatic resolutionAbsolute configuration: (R)

(R)-Propane-1,2,-diolC3H8O2[α]D20=+22.4 (c 1.32, CHCl3)Source of chirality: enzymatic resolutionAbsolute configuration: (R)