KAMARUDDIN ET AL 9 CF3CH,SH 13 (14 Scheme 5.DKR of racemic OCH CF. +CF3CH2OH OCH.CF OH (15) (16) (17 In situ racemisation Scheme 6.DKRof (acetate Tohenclacee ( H,0(1eq) (18) 02H CO.E (19 (20 Scheme 7.DKR ofethylester the e of th ction,r hesis of both opis racemic thiob ramethoxy n of sel d monolayers on surlaces re ENZYMATIC ESTERIFICATION Chirality DOI 10.1002/chir
and during the course of the reaction, more enzymes was added. This method allowed the preparation of (19) (e.e. 5 96%) with 80% isolated yield. The DKR of ethyl ester (18) is shown in Scheme 7. ENZYMATIC ESTERIFICATION The reaction of carboxylic acids with alcohols to form ester through a condensation reaction is known as esterifi- cation. Sanfilippo et al.45 reported the synthesis of both atropisomers of racemic thiobiphenyl (2,2’6,6’-tetramethoxybiphenyl-3,3’-diyl) dimethanethiol (21) by DKR process. Atropisomeric biphenyls are used in the design of selfassembled monolayers on surfaces relevant as biosensors. The esterification reaction of racemic thiobiphenyl in the presence of vinyl acetate and Pseudomonas cepacia lipase resulted in the DKR of epimerizing hemithioacetal intermediates (Scheme 8). This group synthesized a new C2- Scheme 4. DKR of (rac)-fenoprofen thioester. Scheme 5. DKR of racemic ibuprofen ester. Scheme 7. DKR of ethyl ester. Scheme 6. DKR of (rac)-2,2,2-trifluoroethyl a-chlorophenyl acetate. 454 KAMARUDDIN ET AL. Chirality DOI 10.1002/chir
(+)-(21) Lipase CAL- R R 22 240 R、 R R H-(CH 3= Yield (%e.e.(%) (CH- 689 n-P ase PS-D 25 (26) 00 Scheme9 DKR flly alcoho by the combination ofipses and [VOOSPha
Scheme 8. Esterification reaction of racemic thiomethanebiphenyl. Scheme 9. DKR of allyl alcohols by the combination of lipases and [VO(OSiPh3)3]