NOVELTY - Preparation of 3-amino-4-(2,4,5-trifluorophenyl)butanoate intermediates (I) involves (a1) reacting (E)-4-(2,4,5-trifluoro-phenyl)-but-2-enoate intermediate (II) with a borating agent in a suitable solvent to obtain 3-boranyl-4-(2,4,5-trifluorophenyl)butanoate intermediate (III), and (b1) converting the intermediate (III) to the intermediate (I).    USE - For the preparation of intermediate which is optionally used in a process for the preparation of (R)-3-amino-1-(3-trifluormethyl-5,6,7,8-tetrahydro(1,2,4)triazol(4,3-a)pyrazin-7-yl)-4-(2,4,5-trifluorphenyl)butan-1-one (sitagliptin) (claimed) that is useful as an anti-diabetic agent.    ADVANTAGE - The present method represents an improvement over the known methodologies, since the reactions are conducted under mild reaction conditions (especially the step to form intermediate (III)) and utilizes inexpensive, simple and commercially available aminating reagents or their precursors. Also the present method produces the intermediate (II) by using a short and simple process. The method is environmentally friendly by using simple, inexpensive and waste-free oxidizing agents. The present method is particularly one-pot protocol which also offers the retention of configuration.    DETAILED DESCRIPTION - Preparation of 3-amino-4-(2,4,5-trifluorophenyl)butanoate intermediates of formula (I) involves (a1) reacting (E)-4-(2,4,5-trifluoro-phenyl)-but-2-enoate intermediate of formula (II) with a borating agent in a suitable solvent to obtain 3-boranyl-4-(2,4,5-trifluorophenyl)butanoate intermediate of formula (III), and (b1) converting the intermediate (III) to the intermediate (I).    R4 and R5=H, optionally chiral 1-12C alkyl (optionally substituted by aryl and/or aryloxy), optionally chiral 1-12C alkyloxy (optionally substituted by aryl), optionally chiral 6-24C aryl (optionally substituted by alkyl and/or alkyloxy), optionally chiral 6-24C aryloxy (optionally substituted by alkyl), benzyl, optionally chiral 2-13C alkaloyl (optionally substituted by aryl), optionally chiral 7-25C aroyl (optionally substituted by alkyl), optionally chiral 2-13C alkoxycarbonyl, optionally chiral 7-25C aryloxycarbonyl or tosyl;    R3=1-6C alkyl;    R1 and R2=1-12C alkyl or 1-12C alkoxy (both optionally substituted by aryl), T1, halides or T2;    T1=6-14C aryl or 6-14C aryloxy (both optionally substituted by alkyl);    T1=optionally a chiral or non-chiral 5 to 10, particularly 5 to 6, membered mono or bicyclic ring (optionally substituted at least one position with 1-12C alkyl and/or 6-14C aryl), or optionally an O-benzenedioxy residue.    The stereogenic center marked with asterisk is either in (R)- or (S)-configuration at marked center, or it is in racemic form. INDEPENDENT CLAIMS are included for the following:    (1) new intermediates of formula (III), their isomers, and the isomer mixtures; and    (2) preparation of the intermediate (II) involving (a2) reacting 1-bromo-2,4,5-trifluoro-benzene (V) with a Grignard compound, or with magnesium in the presence of an activating agent selected from iodine, methyl iodide and/or 1,2-dibromoethane, in a suitable solvent to obtain (2,4,5-trifluorophenyl)magnesium bromide (VI); and (b2) reacting the compound (VI) with a compound of formula X-(E/Z)-CH2-CH=CH-C(O)-OR3 (VII) in a metal catalyzed cross-coupling process using suitable solvent to obtain the intermediate (II).    X=Cl, Br or I (preferably Br).