Boolean Algebra expression conversion in C#

I am working on converting the boolean algebra expression something like this

  NOT(a AND b) = (NOT a) OR (NOT b)
  NOT (a OR b) = (NOT a) AND (NOT b)
  a AND NOT (b AND c) = (EQ a) AND ( ( NOT b) OR ( NOT c) )

But, somehow it is not working for certain conditions like

  NOT a AND b = (NOT a) AND (EQ b)
  a AND NOT b AND NOT c = (EQ a) AND (NOT b) AND (NOT c)

Following is the logic for conversion. Am i doing anything wrong?

public string ExpressionConversion(string expression)
{
    string finalVal = null;
    string currentToken = "";
    bool isNotFound = false;
    List strList = new List();
    StringHelper stringHelper = new StringHelper();
    var values = stringHelper.CleverSplit(expression, ' ', false, true); //function which splits all the elements in the expression
    for (int j = 0; j < values.Length; j++)
    {
        currentToken = values[j].Trim();
        if (string.IsNullOrEmpty(currentToken.Trim()))
            continue;

        if ((j > 0) && currentToken.StartsWith("AND") && values[j - 1].StartsWith("AND"))
            continue;
        if (currentToken.Contains("NOT"))
        {
            isNotFound = true;
            continue;
        }
        if (currentToken.StartsWith("("))
            strList.Add(currentToken);
        else if (currentToken.StartsWith(")"))
        {
            strList.Add(currentToken);
            isNotFound = false;
        }
        else if (currentToken.StartsWith("AND"))
        {
            if (isNotFound)
                strList.Add(" OR ");
            else
                strList.Add(" AND ");
        }
        else if (currentToken.StartsWith("OR"))
        {
            if (isNotFound)
                strList.Add(" AND ");
            else
                strList.Add(" OR ");
        }
        else
        {
            if (isNotFound)
            {
                strList.Add("( NOT " + currentToken + " )");
                if (!expression.Contains("("))
                    isNotFound = false;
            }
            else
                strList.Add("( EQ " + currentToken + " )");
        }
    }
    if (strList.Count > 0)
        finalVal = string.Join(" ", strList);
    return finalVal;
}