Claisen ester condensation

\documentclass{article}
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\begin{document}

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        -[@{sb1}:-30](-[:-90]R)(-[@{hb1}:-30]@{h1}H)
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        -[:-30]OEt
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            =[:30](-[:90]O\rlap{${}^\ominus$})
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\schemestop

\end{document}