We propose an algorithm that is capable to produce open knotted alkanes, polyethylene oxides and peptides with high or low steric energy at will. The proposed method is quite efficient for small chain lengths, where all other methods fail. The results are validated by applying high level ab initio calculations for selected molecular knots (HF, DFT and MP2). These compounds present substantial interest in the design of new high-tech materials with specific properties. (c) 2006 Elsevier B.V. All rights reserved.