NOVELTY - Synthesis of chiral 1,2,3,4-tetrahydropyrrolo (1,2-a) pyrazine compound (I) or (II) comprises taking watermelon peels as raw material; adding into N-amine ethyl pyrrole (1b) or (1c) and aldehyde ketone carbonyl compound; reacting with or without 3 ?A , 4 ?A, or 5?A molecular sieve at - 85 to - 100?oC using organic solvent and chiral phosphonic acid catalyst (1d)-(1g); and condensing to generate imine on molecule asymmetrical to Friedel-Crafts reaction for 5 minutes to 72 hours to obtain pure product.    USE - Synthesis of chiral 1,2,3,4-tetrahydropyrrolo (1,2-a) pyrazine compound used in medicine or as medicine intermediate.    ADVANTAGE - The method produces optical pure 1,2,3,4-tetrahydropyrrolo (1,2-a) pyrazine compound at high yield. It has mild reaction condition, simple operation, high enantiomer selectivity, and environment friendly.    DETAILED DESCRIPTION - Synthesis of chiral 1,2,3,4-tetrahydropyrrolo (1,2-a) pyrazine compounds of formulae (I) or (II) comprises taking watermelon peels as raw material; adding into N-amine ethyl pyrrole of formula (1b) or (1c) and aldehyde ketone carbonyl compound of formula C(=O)R4R5; reacting optionally with 3 ?A , 4 ?A , or 5 ?A molecular sieve at - 85 to - 100?cC using organic solvent and chiral phosphonic acid catalyst of formula (1d)-(1g); and condensing to generate imine on molecule asymmetrical to Friedel-Crafts reaction for 5 minutes to 72 hours to obtain pure product, in which mol ratio N-amine ethyl pyrrole, aldehyde ketone carbonyl compound, and chiral phosphoric acid mol ratio is (1-10):1:(0.001-1).    R1-R3=H, F, Cl, Br, I, 1-16C alkyl, 1-16C alkoxy, 2-16C alkenyl, 2-16C alkynyl, 3-16C cycloalkyl, 3-16C cycloalkenyl, 3-16C alkynyl, 2-16C carbonyl (sic), benzyl, alkyl or 1-16C alkoxy;    R4, R5=H, 1-16C alkenyl, 2-16C alkynyl, 3-16C cycloalkyl, 3-16C cycloalkenyl, 3-16C alkynyl, 1-16C carbonyl, ketone group, ester group, benzyl, aromatic heterocyclyl, group of formula (1a), or substituted aryl;    R6-R8=1-16C alkyl, 1-16C alkoxy, 2-16C carbonyl (sic), benzyl, aromatic heterocyclyl, group (1a), substituted aryl, or carboxy;    R9-R13=H, F, Cl, Br, I, 1-16C alkyl, 1-16C alkoxy, 2-16C alkenyl, 2-16C alkynyl, 3-16C cycloalkyl, 3-16C cycloalkenyl, 3-16C cycloalkynyl, 2-16C carbonyl (sic), benzyl, amino or conjugated aryl comprising naphthyl, anthryl or phenanthryl;    R14, R15=H, 1-15C alkyl, tri(1-16C alkyl) group, or triaryl silicon group;    R16=OH, NH2, NHSO2R17, NHPO(R17) or NHPO(OR17);and    R17=1-16C alkyl or perfluoroalkyl, 1-16C alkoxy, 2-16C carbonyl (sic), benzyl, aromatic heterocyclyl or group (1a);    aryl=phenyl or naphthyl, and    aromatic heterocyclyl=5-10C heteroaryl containing N, O or S heteroatom.