###$\ce{C18H20}$ : 145 characters

I was curious as to the isomer with the longest name that had actually been reported in the literature rather than hypothetically proposed (so we at least know it exists).

The IUPAC name, whilst not quite as long as some of the examples, is a respectable 145 characters, largely due to the representation of stereochemistry and connectivity.

(2aR,4aR,4bS,6aS,8aR,8bS)-1,2,7,8-Tetramethyl-2a,4a,4b,6a-tetrahydrocyclobuta[a]cyclobuta[2',3']cyclopenta[1',2':3,4]cyclobuta[1,2-b]cyclopentene

The molecule was reported in a 2002 paper (J. Org. Chem. 2002, 67 4436–4440) on the rearrangements of a set of spiro[2.4]hepta-1,4,6-trienes

$\ce{C18H20}$ : 145 characters

I was curious as to the isomer with the longest name that had actually been reported in the literature rather than hypothetically proposed (so we at least know it exists).

The IUPAC name, whilst not quite as long as some of the examples, is a respectable 145 characters, largely due to the representation of stereochemistry and connectivity.

(2aR,4aR,4bS,6aS,8aR,8bS)-1,2,7,8-Tetramethyl-2a,4a,4b,6a-tetrahydrocyclobuta[a]cyclobuta[2',3']cyclopenta[1',2':3,4]cyclobuta[1,2-b]cyclopentene

The molecule was reported in a 2002 paper (J. Org. Chem. 2002, 67 4436–4440) on the rearrangements of a set of spiro[2.4]hepta-1,4,6-trienes