S-ethyl-2(tert-butoxycarbonylamino)-4-methyl-pentanethioate (Boc-Leu-SEt) was synthesized by the mixed anhydride method IBCF/HOBt. The product obtained was characterized by 1H NMR, MS, and IR techniques, and finally confirmed by X-ray diffraction method. The compound crystallizes in the orthorhombic space group P212121 with cell parameters a=9.674(8)angstrom, b=10.659(7)angstrom, c=16.219(13)angstrom with Z=4. The structure exhibits both inter and intramolecular hydrogen bonds of the type N-H center dot center dot center dot O and C-H center dot center dot center dot O. The molecule possesses a chiral center at C9.