A novel method has been found to produce 2,2'-anhydro-1-(.beta.-L-arabinofuranosyl)thymine as a novel useful intermediate compound. A novel method has been further found to produce thymidine from 2,2'-anhydro-1-(.beta.-L-arabinofuranosyl)thymine. According to these methods, synthesis of various L-nucleic acid derivatives, synthesis of which has been difficult till now, is possible.