A portable and collapsible cabana structure is provided to enable ease of carrying to the beach or pool site, ease of assembly and ease of collapse, after use, to again enable ease of portability. An intermediate for the production of an HIV protease inhibitor can be produced from L-phenylalanine. The signal compressing circuit compresses an electrical signal into one pair of wires. In order to provide for an easy manufacture and operation of the space holder the stop is formed by a member having an outer contour corresponding to the inner contour of the jacket and nose-like projections for engaging the recesses are provided at those locations of the periphery of the stop which correspond to the recesses.