MT-45 is a piperazine derivative with potent analgesic activity comparable to morphine despite being structurally unrelated to most other opioids. (R)-(?)-MT-45 is an enantiomer of MT-45 that displays less analgesic potency than that of morphine or the (S)-(+) enantiomer s a piperazine derivative with potent analgesic activity comparable to morphine despite being structurally unrelated to most other opioids. (R)-(?)-MT-45 is an enantiomer of MT-45 that displays less analgesic potency than that of morphine or the (S)-(+) enantiomer s a piperazine derivative with potent analgesic activity comparable to morphine despite being structurally unrelated to most other opioids. (R)-(?)-MT-45 is an enantiomer of MT-45 that displays less analgesic potency than that of morphine or the (S)-(+) enantiomer s a piperazine derivative with potent analgesic activity comparable to morphine despite being structurally unrelated to most other opioids. (R)-(?)-MT-45 is an enantiomer of MT-45 that displays less analgesic potency than that of morphine or the (S)-(+) enantiomer s a piperazine derivative with potent analgesic activity comparable to morphine despite being structurally unrelated to most other opioids. (R)-(?)-MT-45 is an enantiomer of MT-45 that displays less analgesic potency than that of morphine or the (S)-(+) enantiomer s a piperazine derivative with potent analgesic activity comparable to morphine despite being structurally unrelated to most other opioids. (R)-(?)-MT-45 is an enantiomer of MT-45 that displays less analgesic potency than that of morphine or the (S)-(+) enantiomer s a piperazine derivative with potent analgesic activity comparable to morphine despite being structurally unrelated to most other opioids. (R)-(?)-MT-45 is an enantiomer of MT-45 that displays less analgesic potency than that of morphine or the (S)-(+) enantiomer s a piperazine derivative with potent analgesic activity comparable to morphine despite being structurally unrelated to most other opioids. (R)-(?)-MT-45 is an enantiomer of MT-45 that displays less analgesic potency than that of morphine or the (S)-(+) enantiomer s a piperazine derivative with potent analgesic activity comparable to morphine despite being structurally unrelated to most other opioids. (R)-(?)-MT-45 is an enantiomer of MT-45 that displays less analgesic potency than that of morphine or the (S)-(+) enantiomer s a piperazine derivative with potent analgesic activity comparable to morphine despite being structurally unrelated to most other opioids. (R)-(?)-MT-45 is an enantiomer of MT-45 that displays less analgesic potency than that of morphine or the (S)-(+) enantiomer s a piperazine derivative with potent analgesic activity comparable to morphine despite being structurally unrelated to most other opioids. (R)-(?)-MT-45 is an enantiomer of MT-45 that displays less analgesic potency than that of morphine or the (S)-(+) enantiomer s a piperazine derivative with potent analgesic activity comparable to morphine despite being structurally unrelated to most other opioids. (R)-(?)-MT-45 is an enantiomer of MT-45 that displays less analgesic potency than that of morphine or the (S)-(+) enantiomer s a piperazine derivative with potent analgesic activity comparable to morphine despite being structurally unrelated to most other opioids. (R)-(?)-MT-45 is an enantiomer of MT-45 that displays less analgesic potency than that of morphine or the (S)-(+) enantiomer s a piperazine derivative with potent analgesic activity comparable to morphine despite being structurally unrelated to most other opioids. (R)-(?)-MT-45 is an enantiomer of MT-45 that displays less analgesic potency than that of morphine or the (S)-(+) enantiomer s a piperazine derivative with potent analgesic activity comparable to morphine despite being structurally unrelated to most other opioids. (R)-(?)-MT-45 is an enantiomer of MT-45 that displays less analgesic potency than that of morphine or the (S)-(+) enantiomer s a piperazine der