sentences:  There are four symmetrical isomers of DBT which can be made, or ten isomers in total if unsymmetrical substitution is used.Of these only the n-butyl analogue DBT is known to be active in humans; the isobutyl, sec-butyl, and tert-butyl isomers DIBT, DSBT and DTBT have never been tested and only DBT and DIBT were made by Shulgin.The unsymmetrical isomers BIBT, BSBT, BTBT, IBSBT, IBTBT and SBTBT are also possible but have never been made and no predictions have been made about their activity.