Crystal structures of two 1,2,3,4-tetra-hydro-naphthalenes obtained during efforts towards the total synthesis of elisabethin A.

The two substituted 1,2,3,4-tetra-hydro-naphthalenes, methyl ( R )-3-{(1 R ,4 S )-6-meth-oxy-4,7-dimethyl-5,8-bis-[(triiso-propyl-sil-yl)-oxy]-1,2,3,4-tetra-hydro-naph-th-al-en-1-yl}butano-ate, C 36 H 66 O 5 Si 2 , ( 2 ), and methyl ( E )-3-{(1 R ,4 S )-8-hy-droxy-6-meth-oxy-4,7-dimethyl-5-[(triiso-propyl-sil-yl)-oxy]-1,2,3,4-tetra-hydro-naphthalen-1-yl}acrylate, C 26 H 42 O 5 Si, ( 8 ), crystallize in the Sohncke space groups P 2 1 2 1 2 1 and P 2 1 , respectively, with the absolute structure determined on the basis of anomalous dispersion effects. The configurations of the stereo centres in the 1,2,3,4-tetra-hydro-naphthalene moiety of ( 2 ) and ( 8 ) are the same, and the conformation of the non-aromatic part of the ring system is nearly identical. In the crystal of ( 2 ), weak non-classical C-H⋯O inter-actions consolidate the packing, whereas in ( 8 ), inter-molecular O-H⋯O hydrogen-bonding inter-actions of medium-to-weak strength direct the mol-ecules into Z -shaped strands extending parallel to [010].