Helical primary structures of four-membered rings: (M)-trispiro[3.0.0.3.2.2]tridecane

The synthesis of (NI)-trispiro[3.0.0.3.2.2]tridecane [(M)-4], the first hydrocarbon with a helical primary structure of four-membered rings, is described. Key step is the kinetic resolution of a cyclobutanone through reduction with bakers' yeast. As compared to its analogue of three-membered rings, (M)-trispiro[2.0.0.2.1.1]nonane [(M)-1], the specific rotation of (M)-4 is cut in three. According to molecular mechanics calculations this could be due to a potential to adopt different conformations, not given in (M)-1, and to the fact, that (M)-4 describes a distinctly shorter section of a helix than (M)-1. (C) 2003 Elsevier Science Ltd. All rights reserved.