The present invention relates to compounds having a structure according to Formula I wherein n, m, z, R, R2, R3, R4, R5, R6, A, E, X, Y, a and b are as defined above; or an optical isomer, diastereomer or enantiomer thereof; a pharmaceutically acceptable salt, hydrate, or prodrug thereof. As a result, it is possible to maximize gas compression efficiency by minimizing leakage of high pressure gas . A reference support that is attachable to or movable along a hollow object has a display face presenting and supporting a plurality of scannable reference targets.