STRUCTURES OF 2 DIASTEREOMERIC ALDOL PRODUCTS FROM A NEW SILICON-DIRECTED CONDENSATION

Hexahydro-3,3,6-trimethyl-5-phenyl-1H,7H-pyrrolo[2,1-e][1,3,6,2]dioxazasilonin-7-one, C17H25-NO3Si, M(r) = 319.48. (2S,3R)-anti-Diastereomer (I), orthorhombic, P2(1)2(1)2(1), a = 8.716 (4), b = 11.677 (3), c = 17.161 (6) angstrom, V = 1746 (1) angstrom 3, Z = 4, D(x) = 1.22 g cm-3, lambda(Mo K-alpha) = 0.71073 angstrom, mu = 1.50 cm-1, F(000) = 688, room temperature, final R = 0.040 for 1683 reflections with F(o)2 > 0. (2S,3S)-syn-Diastereomer (II), monoclinic, P2(1), a = 6.633 (2), b = 14.645 (3), c = 9.630 (2) angstrom, beta = 109.96 (2)-degrees, V = 879.3 (4) angstrom 3, Z = 2, D(x) = 1.21 g cm-3, lambda(Mo K-alpha) = 0.71073 angstrom, mu = 1.49 cm-1, F(000) = 344, room temperature, final R = 0.042 for 2537 reflections with F(o)2 > 0. The compounds have a nine-membered heterocyclic ring containing the Si atom, the N atom of the pyrrolidine ring, two O atoms bonded to silicon and a carbonyl C atom. Bond distances in the molecules are normal and equivalent bonds are equal within three times their e.s.d.'s. Isomer (I) shows a disorder in the pyrrolidine ring that is absent in isomer (II).