74497-15-7Relevant articles and documents
Optimization of the use of a chiral bio-based building block for the manufacture of DHPPA, a key intermediate for propionate herbicides
Fleer, Michel P. M.,Verkuijl, Bastiaan J. V.
, p. 3993 - 3998 (2014/08/05)
An alternative route for the production of (R)-2-(4-hydroxyphenoxy) propionic acid (DHPPA), a key intermediate in herbicide chemistry, is proposed. This route makes use of a chiral building block, initially produced by fermentation. The route has been optimized based on two steps: chlorination and etherification. The chlorination step has a maximum ee of 99% and a yield of 85% after distillation. The etherification step has a yield of 66%. Comparison of the route with the industrial standard shows a significant improvement in terms of green chemistry: waste streams are lowered up to 7-fold and the toxicity of the waste streams is reduced. This journal is the Partner Organisations 2014.
Synthesis of enantiomerically pure (R)- and (S)-2-sulfanylpropanoic acids ('thiolactic acid') from ethyl (S)-lactate using pig liver esterase
Hof, Robert P.,Kellogg, Richard M.
, p. 1247 - 1250 (2007/10/02)
The methanesulfonates of optically pure ethyl (S)-lactate or ethyl (R)-2-chloropropanoate 5, obtained with inversion of configuration from ethyl (S)-lactate on treatment with SOCl2, can be substituted by caesium thiolates with inversion of configuration to yield (R) and (S) ethyl 2-(acetylsulfanyl)propanoate, 2a and 2b, respectively.Hydrolysis of the carboxy ester of 2a, 2b to the acid under common acidic or basic conditions always leads to substantial racemisation.However, the use of the mild biocatalyst pig liver esterase (PLE) at neutral pH yields the carboxylic acids 4a and 4b without racemisation.The acetylsulfanyl group remains unaffected during this process.Subsequent treatment of the acetylsulfanyl group of 4a or 4b with 2 mol dm-3 aqueous ammonia leads to the useful optically pure building block (R)- or (S)-2-sulfanylpropanoic acid ('thiolactic acid') 3a, 3b in an overall yield of 65percent based on cheap ethyl (S)-lactate.