Passing on a variable to Julia run() command


I am new to running API calls in general but I would like to use Julia to run API calls.

Here, I am trying to run the curl command from Julia using run( ):

reactants=""" "C(O)1=C(O)C=C(C2=C(O)C=C([H])C([H])=C2C2=C([H])C=C([H])C=C2)C=C1O.[H].[H].[H]" """
run(`curl --data '{ "reactants" :
$reactants, "mol":"" }' 
    --header "Content-Type: application/json" 
    --header "Authorization:$API_key" 
    -X POST $call`)

I am trying to use “$” to refer to the variables created outside of this command. $API_key and $call create no problems, but when I use $reactants instead of the string it stands for, I get an empty result from this curl command.

This is an example of this curl command from the manual for this type of API calls:

curl --data '{ "reactants" :
"C(O)1=C(O)C=C(C2=C(O)C=C([H])C([H])=C2C2=C([H])C=C([H])C=C2)C=C1O.[H].[H].[H]", "mol":"" }' --header "Content-Type: application/json" 
--header "Authorization:apk-have-here-your-own-key" 

Could someone suggest why do I use “$” wrong and if there is a better way?

Thank you!