ÃÂ<sup>4</sup>-Tetrahydrocannabinol (Delta-4-THC, ÃÂ<sup>4</sup>-THC, ÃÂ<sup>6a(7)</sup>-THC) is a synthetic isomer of tetrahydrocannabinol, developed in the 1970s during research to develop improved synthetic routes to the natural forms ÃÂ<sup>8</sup>-THC and ÃÂ<sup>9</sup>-THC. Only the (9R, 10aR) enantiomer has been synthesised, though other isomers are possible.