Connect atoms with chemfig in nested rings

Question

I'm trying to draw a cylindrospermopsin molecule using chemfig. There's my code

\documentclass[12pt]{standalone}
\pagestyle{empty}
\usepackage{standalone} 
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{makeidx}
\usepackage{graphicx,graphics}
\usepackage[brazil]{babel}
\usepackage{chemfig}
\begin{document}
\chemfig{%
A*6(-B*5(-R-S-\phantom{G}-\phantom{C})-C*6(-G-H-I(-K-[:-30]L*6(-M-N-O-P-Q=\phantom{L}))-J-\phantom{D})-D-E-F-)
}
\end{document}

I'm getting the following molecule

There's a way to link the S and G atoms correctly and make a single chemical bond between C and G

This is the entire cylindrospermopsin structure

Answer 1

Use hooks (? in chemfig's notation):

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{chemfig}
\begin{document}

\chemfig{*6(-(-[:-72]?)-*6(-(-[:-108]?)----)----)}

\chemfig{A*6(-B(-[:-72]R?[a])-C*6(-G(-[:-108]S?[a])-H-I-J?[b])-D?[b]-E-F-)}

\end{document}