Precursors of the RNA World in Space: Detection of (Z)-1,2-ethenediol in the Interstellar Medium, a Key Intermediate in Sugar Formation

We present the first detection of (Z)-1,2-ethenediol, (CHOH)(2), the enol form of glycolaldehyde, in the interstellar medium toward the G+0.693-0.027 molecular cloud located in the Galactic Center. We have derived a column density of (1.8 +/- 0.1) x 10(13) cm(-2), which translates into a molecular abundance with respect to molecular hydrogen of 1.3 x 10(-10). The abundance ratio between glycolaldehyde and (Z)-1,2-ethenediol is similar to 5.2. We discuss several viable formation routes through chemical reactions from precursors such as HCO, H2CO, CHOH, or CH2CHOH. We also propose that this species might be an important precursor in the formation of glyceraldehyde (HOCH2CHOHCHO) in the interstellar medium through combination with the hydroxymethylene (CHOH) radical.