definiens: means the compound having the systematic ( IUPAC ) name [ 3S- [ 3R*[E(1S*,3S*,4S*)],4S*,5R*,8S*,9E,12R*,14R*,15S *, 16R*,18S*,19S*,26aR*]]- 5,6,8,11,12,13,14,15,16,17,18,19,24,25,26,26a - hexad ecahydro-5,19 - dihydroxy- 3-[2-(4 - hydroxy-3 - methoxycyclohexyl)-1 - methylethenyl]-14,16 - dimethoxy -4,10, 12,18 - tetramethyl-8-(2 - propenyl)-15,19 - epoxy -3H - pyrido[2,1 - c][1,4 ] oxaazacyclotricosine-1,7,20,2 1(4H,23H)-tetrone, monohydrate and also may be refe rred to as FK506 or SPI-026