Please cite this article in press as: K. Asokan, et al., Applications of 2, 2, 2 trifluoroethanol as a versatile co-solvent in supercritical fluid chromatography for purification of unstable boronate esters, enhancing throughput, reducing epimerization, and for additive free purifications, J. Chromatogr. A (2017), https://doi.org/10.1016/j.chroma.2017.11.031 ARTICLE IN PRESS G Model CHROMA-359015; No. of Pages 9 Journal of Chromatography A, xxx (2017) xxx–xxx Contents lists available at ScienceDirect Journal of Chromatography A j o ur na l ho me page: www.elsevier.com/locate/chroma Full length article Applications of 2, 2, 2 trifluoroethanol as a versatile co-solvent in supercritical fluid chromatography for purification of unstable boronate esters, enhancing throughput, reducing epimerization, and for additive free purifications Kathiravan Asokan a , Khaja Mohinddin Shaikh a , Shahaji Sopan Tele a , Siddheshwar Kisan Chauthe a , Shabana Ansar b , Muthalagu Vetrichelvan b , Roshan Nimje b , Anuradha Gupta b , Arun Kumar Gupta b , Ramakanth Sarabu a , Dauh-Rurng Wu c , Arvind Mathur c , Lakshmikant Bajpai a,∗ a Discovery Analytical Sciences, BMS-Biocon Research Centre, Bangalore, India b Department of Discovery Synthesis, BMS-Biocon Research Centre, Bangalore, India c Department of Discovery Synthesis, Bristol-Myers Squibb Company, Princeton, NJ, USA a r t i c l e i n f o Article history: Received 30 June 2017 Received in revised form 13 November 2017 Accepted 14 November 2017 Available online xxx Keywords: SFC TFE Boronate esters Degradation Epimerization a b s t r a c t Analysis and purification of boronic acid pinacol esters by RPLC is very challenging due to their degra- dation in aqueous and alcoholic solvents. These compounds are difficult to purify by SFC too as they are equally sensitive to traditional co-solvents like methanol, ethanol, and 2-propanol. 2,2,2 trifluo- roethanol (TFE), which has been reported for the purification of a few alcohol sensitive compounds, was evaluated as a co-solvent in this study for the purification of chiral and achiral boronate esters by SFC. Examples of twelve compounds were presented in this paper where degradation of boronic acid pinacol esters was successfully controlled by replacing methanol with TFE as the co-solvent in SFC. A separate study showed that TFE can also control the epimerization of the enantiomers of 3 substituted 1,4 benzodiazepine analogues during the purification process. In addition to above benefits, 2,2,2tri- floroethanol showed improved selectivity and resolution for most of the compounds. With its stronger solvent strength compared to other alcohols, TFE could also be used to reduce the co-solvent percentage needed for elution and to shorten retention time of highly polar samples which did not elute even in 50% of other co-solvents in SFC. A case study of compound B demonstrated that TFE provided a reduced co-solvent percentage and a shorter cycle time with much improved resolution as compared to methanol, thus resulting in higher loading and throughput with reduction of total solvent consumption. © 2017 Elsevier B.V. All rights reserved. 1. Introduction Boron-containing organic compounds have found widespread use in synthetic organic and medicinal chemistry [1]. More recently, boronic acid-containing polymers have proven valuable in a variety of biomedical applications, including the treatment of HIV, obesity, diabetes, and cancer [2]. Interactions of boronic acids with diols and strong Lewis bases such as fluoride or cyanide anions lead to their utility in various sensing applications [3,4]. ∗ Corresponding author at: Discovery Analytical Sciences, BMS-Biocon Research Centre, Syngene International Ltd, Plot No.2 & 3, Bommasandra IV Phase, Jigani Link Road, Bangalore, 560 099, India. E-mail address: lkbajpai@hotmail.com (L. Bajpai). Boronic acids are widely used in Suzuki-Miyaura reaction as nucleophilic agent for the C C bond formation [5–8]. Suzuki coupling is becoming an attractive tool for synthesis as boron com- pounds are easy to use and their by-products are less toxic, easy to purge from reaction mixtures and ultimately converting into environment-friendly boric acid [9]. However, boronic acids are unstable and undergo degradation through the pathways like oxi- dation, photodeboronation, polymerisation and tendency to exist as oligomeric anhydrides [10,11]. To overcome this instability, boronic acids have been masked by electron donating group like pinacol to make the corresponding ester. Pinacol masked boronic acids are relatively stable to air, moisture and do not require any deprotection step in Suzuki coupling [10,12,13]. Analysis and purification of boronic acid pinacol ester are chal- lenging by HPLC due to its ready conversion to boronic acid in https://doi.org/10.1016/j.chroma.2017.11.031 0021-9673/© 2017 Elsevier B.V. All rights reserved.