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In the synthesis of lactose acceptor that will be used to take part of oligisacarides and glicoconjugate it is necessary the protection of the 3',4' lactose positions with the isopropylidene group. In the chemical reaction, several collateral products are also obtained that must be separated from the isomer of interest. Two chromatographic column purifications and one final crystallization have been reported. In this work, the first chromatographic purification is replaced by two extractions: one liquid-liquid and one solid-liquid. Besides, an experimental design was also made to identify the best operation conditions for the extractions. In the liquidliquid extraction dichloromethane was used with a liquid-liquid ratio at level +1 and a stirring speed at level +1. The operation was repeated eight times. In the solid-liquid extraction, acetone was used with a liquid-solid ratio at level +1 and a stirring speed at level -1. The operation was repeated 12 times. The purification method described in the literature and the method proposed in the present work were compared, and both obtained similar amounts of the mixture of the 3 ', 4' and 4 ', 6' isopropylidene lactose isomers. Following the proposed method, the results are obtained in a shorter time and with a notable reduction in the consumption of reagents. [ABSTRACT FROM AUTHOR]