... Tetrahedron: Asymmetry. Volume 17, Issue 16, 25 September 2006, Pages 2393–2400. ... Several synthetic procedures for the preparation of Dip, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28 and 29 either in racemic 14, 16, 17, 18, 19, 20 and 21 or enantiomerically pure ...