... Tetrahedron Letters. Volume 28, Issue 11, 1987, Pages 1195–1198. Cover image Cover image. Acetals and ketals of 2-(2-pyridyl)propane-1,3-diol novel protection for carbonyl groups. ... References. 1; AR Katritzky, GR Khan, OA Schwarz; Tetrahedron Lett. (1984), p. 1223. ...