. . "Thus group R may be a saturated or unsaturated heterocyclic or heterocyclic alkylene group, e.g. of 3-8 carbons and at least one, e.g. one or two ring heteroatoms selected from 0, N and S, especially 0 and/or N, examples of such groups are furyl, tetrahydrofuryl, furfuryl and tetrahydrofurfuryl, pyranyl and tetra hydropyranyl." . .