The tris-onium ethers (XIII, A and B) and the tetra-onium ethers (XV A, B and C), together with the corresponding polymethylene tris-onium (XIV A and B) and polymethylene tetra- onium compounds (XVI, A, B and C), have been synthesised. Replacement of a methylene group in the inter-onium polymethylene chain by an ether link almost always lowers muscle relaxant potency.
