The first report on the detection of hydroxyethanal, CH₂OHCHO, aka glycolaldehyde, in the interstellar medium was met with great enthusiasm as this molecule represents a more complex precursor to sugars than the ubiquitous methanal, H₂CO, aka formaldehyde. Very recently, there has been a report on the detection of 1,3-dihydroxypropanone in Sgr B2(N-LMH):
S. L. Widicus Weaver and G. A. Blake,
1,3-Dihydroxyacetone in Sagittarius B2(N-LMH): The First Interstellar Ketose
Astrophys. J. 624, L33–L36 (2005);
Erratum
Astrophys. J. 632, L163 (2005).
A column density was derived that was very high: about a factor of three higher than that of H₂CO – that seems rather peculiar.

One more recent paper seriously questions the findings mentioned above:
A. J. Apponi, D. T. Halfen, L. M. Ziurys, J. M. Hollis, A. Remijan, and F. J. Lovas,
Investigating the Limits of Chemical Complexity in Sagittarius B2(N): A Rigorous Attempt to Confirm 1,3-Dihydroxyacetone
Astrophys. J. 643, L29–L32 (2006).
No line was identified unambiguously. The upper limit derived for 1,3-dihydroxypropanone was lower than the column density derived above by a factor of about 300 and about a factor of four below that of hydroxyethanal. Moreover, it was pointed out that the column density of 1,3-dihydroxypropanone may be lower still by about a factor of six or so if the column density ratio 1,3-dihydroxypropanone : hydroxyethanal corresponds to that of hydroxyethanal : methanal. Even though this does not have to be correct this assumption is certainly reasonable.

Overall, we would recommend to view 1,3-dihydroxypropanone as not yet detected.

1,2-Dihydroxypropanal, aka glyceraldehyde, is an isomer of 1,3-dihydroxypropanone. It has been searched for unsuccessfully by:
J. M. Hollis, P. R. Jewell, F. J. Lovas, A. Remijan, and H. Møllendal,
Green Bank Telescope Detection of New Interstellar Aldehydes: Propenal and Propanal
Astrophys. J. 610, L21–L24 (2004).
The upper limit for 1,2-dihydroxypropanal is similar to that of 1,3-dihydroxypropanone in the paper above.

Contributor(s): H. S. P. Müller; 05, 2006