Solid-phase synthesis of enantio-controlled lactic acid oligomers
摘要:
A synthetic method for lactic acid oligomers via solid-phase synthesis under mild reaction conditions with up to 99% yield is presented. The fine control of the chirality on each lactic acid unit of the oligomers was easily achieved by the substitution of (R)-THP-protected lactic acid (R)-2 by (S)-2 without alternating the procedure. The overall synthesis of the trimer and tetramer was completed in one and two days, respectively. Intramolecular cyclizations of enantio-controlled lactic acids were also attempted through the Yamaguchi macrolactonization or the Mitsunobu reaction. However, we were unable to isolate single cyclic oligomers but always obtained a mixture of cyclic oligomers. (C) 2011 Elsevier Ltd. All rights reserved.
A method of treating a subterranean formation at temperatures of at least 150° C. is disclosed. The method comprises introducing a pressurized fracturing liquid comprising proppants and solid channelants to create fractures in the subterranean formation, wherein the channelants comprise polylactic acid (PLA) solids derived from a blend of poly L-lactic acid (PLLA) and poly D-lactic acid (PDLA).