// first we create a transaction
var tx = new Transaction()
  .from(utxo)
  .to(toAddress, 100000)
  .sign(privateKey);

// we then extract the signature from the first input
var inputIndex = 0;
var signature = tx.getSignatures(privateKey)[inputIndex].signature;

var scriptSig = Script.buildPublicKeyHashIn(publicKey, signature);
var flags = Interpreter.SCRIPT_VERIFY_P2SH | Interpreter.SCRIPT_VERIFY_STRICTENC;
var verified = Interpreter().verify(scriptSig, scriptPubkey, tx, inputIndex, flags);