Organic Structure Challenge

Recently we had this challenge in our Organic Chemistry Department.
I was not involved in it but I thought it might be interesting for the SE Chemistry site, so here it is.


Propose a structure for C20H18 with the longest IUPAC name.
Following rules apply:


1. Names must be generated with MarvinSketch: Structure>Generate Name…>Preferred IUPAC Name (<https://www.chemaxon.com/products/marvin>).
2. No isotopic markings can be used.
3. The structures must be possible (no cycles with too much unsaturations nor systems with impossible tension).
4. All the characters will be counted: numbers, letters, points, colons, dashes, everything.
5. Longest name wins.


Here is the example that was given:


[![enter image description here](https://i.stack.imgur.com/h7qY0.png)](https://i.stack.imgur.com/h7qY0.png)


and the name provided by MarvinSketch:


(1'*R*,4'*Z*,6'*Z*,8'*Z*,10'*Z*,12'*S*,15'*R*,16'*R*,17'*R*)-spiro[cyclopropane-1,18'-tetracyclo[13.2.1.04,17.012,16]octadecane]-2,2',4',6',8',10',13'-heptaene


**141 characters**


Good luck and prosperous year 2018!


**EDIT**


Well, what is a challenge without a prize?
So, I have set a bounty worth +50 reputation for the longest name.
Sorry, I can not spend much more on it.
Remember that you can post more than one structure.
If you have proposed one and after some days you find a structure with a longer name, you can post it too.




$\ce{C20H18}$, 246 characters
-----------------------------



> 
> [![enter image description here](https://i.stack.imgur.com/9k3Lt.png)](https://i.stack.imgur.com/9k3Lt.png)
> 
> 
> `InChI=1S/C20H18/c1-2-13(1)5-15(13)7-17(15)9-19(17)11-12(19)20(11)10-18(20)8-16(18)6-14(16)3-4-14/h1-4,11-12H,5-10H2/t11-,12+,15-,16-,17-,18-,19-,20-/m1/s1`
> 
> 
> **PIN**: (1'R,1''R,1'''R,1''''R,1'''''R,1''''''R,2''''R,3''''S)-octaspiro[tetrakis(cyclopropane)-1,2':1',2'':1'',2''':1''',4''''-bicyclo[1.1.0]butane-2'''',2''''':1''''',2'''''':1'''''',2''''''':1''''''',1''''''''-tetrakis(cyclopropane)]-2,2''''''''-diene
> 
> 
> 


 16

### $\ce{C20H18}$, 153 characters


`(1'S,2'S,3'R,6'S,8'S)-3'-(cycloprop-2-en-1-yl)-11'-[(cycloprop-2-en-1-yl)methylidene]spiro[cyclopropane-1,7'-tricyclo[6.3.0.02,6]undecane]-2,4',9'-triene`


[![enter image description here](https://i.stack.imgur.com/6mmlC.png)](https://i.stack.imgur.com/6mmlC.png)




---


P. S. I guess someone should just start, so I simply used the slightly modified structure from the example. I'm pretty sure this one is going to be criticized a lot by experienced organic chemists, so it's more like a kick-starter.


I found it very useful to start with [Avogadro](https://avogadro.cc/) first to sketch (and optimize, `Ctrl+Alt+O`) the initial geometry (very handy for the geometries which are distorted or resembling platonic solids), then import `cml` file to MarvinSketch and do the rest.


For those who would like to check the names, copy it from here, the press `Ctrl+Shift+N`, `Ctrl+V` and click `Import` in MarvinSketch. For the record, currently MarvinSketch 17.29.0 is being used.


 15

### $\ce{C18H20}$ : 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](https://i.stack.imgur.com/i1GKU.png)](https://i.stack.imgur.com/i1GKU.png)
> 
> 
> `(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


 12

Here is my input with character count increasing up to down. I have added InChI codes because it seems MarvinSketch is less capable of reading names than it is in their generation.


### 1. $\ce{C20H18}$: 164 characters



> 
> [![enter image description here](https://i.stack.imgur.com/YYrdM.png)](https://i.stack.imgur.com/YYrdM.png)
> 
> 
> * `InChI=1/C20H18/c1-11-3-4-12(2)17-16-9-15-13(11)5-6-14(15)18(17)20(16)10-19(20)7-8-19/h3-6,9,13,15H,1,7-8,10H2,2H3/b4-3-,17-12+/t13-,15+,20-/s2`
> * **PIN**: (2'*R*,4''*Z*,7''*S*,11''*S*)‐3''‐methyl‐6''‐methylidenedispiro[bis(cyclopropane)‐1,1':2',14''‐tetracyclo[8.4.0.02,13.07,11]tetradecane]‐1''(10''),2'',4'',8'',12''‐pentaene
> 
> 
> 


### 2. $\ce{C20H18}$: 167 characters



> 
> [![enter image description here](https://i.stack.imgur.com/8FT1y.png)](https://i.stack.imgur.com/8FT1y.png)
> 
> 
> * `InChI=1/C20H18/c1-11-3-4-12(2)17-16-9-15-13(11)5-6-14(15)18(17)20(16)10-19(20)7-8-19/h3-8,14-15,18H,2,9-10H2,1H3/b4-3-,13-11-/t14-,15+,18+,20+/s2`
> * **PIN**: (2'*S*,2''*R*,3''*S*,7''*R*,11''*R*)‐3''‐methyl‐6''‐methylidenedispiro[bis(cyclopropane)‐1,1':2',14''‐tetracyclo[8.4.0.02,13.07,11]tetradecane]‐1''(10''),2,4'',8'',12''‐pentaene
> 
> 
> 


### 3. $\ce{C20H18}$: 169 characters



> 
> [![enter image description here](https://i.stack.imgur.com/iKSXh.png)](https://i.stack.imgur.com/iKSXh.png)
> 
> 
> * `InChI=1/C20H18/c1-11-3-4-12(2)17-16-9-15-13(11)5-6-14(15)18(17)20(16)10-19(20)7-8-19/h3-6,9,14,18H,2,7-8,10H2,1H3/b4-3-,13-11-/t14-,18+,20+/s2`
> * **PIN**: (1''*S*,2'*S*,4''*Z*,6''*Z*,10''*S*)‐6''‐methyl‐3''‐methylidenedispiro[bis(cyclopropane)‐1,1':2',14''‐tetracyclo[8.4.0.02,13.07,11]tetradecane]‐2''(13''),4'',6'',8'',11''‐pentaene
> 
> 
> 


### 4. $\ce{C20H18}$: 171 characters



> 
> [![enter image description here](https://i.stack.imgur.com/wY4s0.png)](https://i.stack.imgur.com/wY4s0.png)
> 
> 
> * `InChI=1/C20H18/c1-11-3-4-12(2)17-16-9-15-13(11)5-6-14(15)18(17)20(16)10-19(20)7-8-19/h3-6,9,13,15H,1,7-8,10H2,2H3/b4-3-,17-12+/t13-,15+,20-/s2`
> * **PIN**: (1''*S*,2'*S*,4''*Z*,6''*Z*,10''*R*,11''*R*)‐6''‐methyl‐3''‐methylidenedispiro[bis(cyclopropane)‐1,1':2',14''tetracyclo[8.4.0.02,13.07,11]tetradecane]‐2,2''(13''),4'',6'',8''‐pentaene
> 
> 
> 


### 5. $\ce{C20H18}$: 172 characters



> 
> [![enter image description here](https://i.stack.imgur.com/tkIdU.png)](https://i.stack.imgur.com/tkIdU.png)
> 
> 
> * `InChI=1/C20H18/c1-11-3-4-12(2)17-16-9-15-13(11)5-6-14(15)18(17)20(16)10-19(20)7-8-19/h3-9,14-15,17-18H,2,10H2,1H3/b4-3-,13-11-/t14-,15+,17+,18+,20+/s2`
> * **PIN**: (1''*S*,2'*R*,2''*S*,4''*Z*,6''*Z*,10''*R*,11''*S*)‐6''‐methyl‐3''‐methylidenedispiro[bis(cyclopropane)‐1,1':2',14''‐tetracyclo[8.4.0.02,13.07,11]tetradecane]‐2,4'',6'',8'',12''‐pentaene
> 
> 
> 


 10

[![enter image description here](https://i.stack.imgur.com/giGUV.png)](https://i.stack.imgur.com/giGUV.png) \*\*162 Characters


[![enter image description here](https://i.stack.imgur.com/VoT1U.jpg)](https://i.stack.imgur.com/VoT1U.jpg)


* PIN:(1'S,2'S,6'S,7'R,12'S,14'S)‐7'‐methyldispiro[cyclopropane‐1,8'‐pentacyclo[7.5.1.02,6.02,14.012,15]pentadecane‐
13',1''‐cyclopropane]‐2,2'',3',9'(15'),10'‐
pentaene
* I have used MarvinSketch 17.28.0 for generating pin.


 6

### $\ce{C20H18}$, 290 characters


Heavily based on [Daniel Bonniot de Ruisselet](https://chemistry.stackexchange.com/users/57098/daniel-bonniot-de-ruisselet)'s [idea](https://chemistry.stackexchange.com/a/88235/544), the two "spiraned" cyclopropane pairs next to ending cyclopropenes are fused to bicyclobutanes as well, allowing remaining methyls attachment to the ending cyclopropenes, thus also allowing more chiral centers.



> 
> [![enter image description here](https://i.stack.imgur.com/8hiZI.png)](https://i.stack.imgur.com/8hiZI.png)
> 
> 
> * **PIN**: (1*S*,1′*R*,1′′′*S*,1′′′′′*R*,2′′*S*,2′′′′*S*,3′*S*,3′′′*S*,3′′′′′*S*,4′*R*,4′′′*R*,4′′′′′*R*)‐2,3′′′′′′‐dimethylhexaspiro[cyclopropane‐1,2′‐bicyclo[1.1.0]butane‐4′,1′′‐cyclopropane‐2′′,2′′′‐bicyclo[1.1.0]butane‐4′′′,1′′′′‐cyclopropane‐2′′′′,2′′′′′‐bicyclo[1.1.0]butane‐4′′′′′,1′′′′′′‐cyclopropane]‐2,2′′′′′′‐diene
> * `InChI=1S/C20H18/c1-7-3-15(7)9-10(15)17(9)5-19(17)13-14(19)20(13)6-18(20)11-12(18)16(11)4-8(16)2/h3-4,9-14H,5-6H2,1-2H3/t9-,10+,11-,12+,13-,14+,15+,16+,17-,18-,19+,20-`
> * CXSMILES: `[H][C@]12C@([C@@]11C=C1C)[C@]21C[C@]11[C@]2([H])[C@@]1([H])[C@]21C[C@@]11[C@@]2([H])[C@]1([H])[C@@]21C=C1C |c:6,32|`
> * gzipped and base64 encoded molfile:
> 
> 
> 
> ```
> H4sIAGimq1sCA6WWTW7CMBCF9znFXKDW/PlvXSqxocsepIuev7YjGhFPGrBRhODl5WPmeWyxANy+
> fyixAGYOlChy5gv8vZYFOIB4AGwXtfftlXOGL0bEpX5Tp4EywJsXlxVT1dCVuwjv8Iiwr0bxjmLQ
> SlEnXsSk8Bllq0VdDH66lvopySgl5ZpGpfh8kAs/VYtUSijPHuSCZ5TgAno56Yifp/xTy2ku0Qnl
> s1xOKcmhKM92tFFm0t0oM7ObXNQUZ2d3o8zsRimU6FeK5zSYS92NjCuF6KAjfKWjcUoutQj/daSj
> HaWoLRd2iqSjHYkEnqW0NbJPqevzFO+yIK5ThwUzRml72p666ytr5JHvp9RjLtdXzjofmO67sa7W
> GGU76xKPpcttp9FOFVPV3r562SRor3pTDUfe0P9abDf23mSqudkNr61mi0BoqtRVViTDWyTqMyMx
> vXr34s5rq31mFID87hgvagKKvVq8fcfFyEbH1Lj7taAKMQhGZWUeeH08PE4fc6eWdll6tRC0J5R6
> fa+m+uewI2iNYtfFDeDj87L8Autmps9wCgAA
> 
> ```
> 
> 
> *(All data according to MarvinSketch 18.23, image postprocessed in a vector image editor; name postprocessed chem.SE and other text editor - RS italicization and apostrophe to prime replacement.  
> 
> Marvin obviously has some issues, importing the produced InChI string produces some unspecified centers, so I have generated ChemAxon SMILES, this when pasted produces different stereochemistry, so I have added a compressed MDL molfile as well)*
> 
> 
> 


Can someone beat 300 characters, by further modifications?


 6