c custom compare function for std sort

Question

I want to create custom compare function for std::sort(), to sort some key-value pairs std::pair

Here is my function

 template <typename K, typename V>
 int comparePairs(const void* left, const void* right){
        if((((pair<K,V>*)left)->first) <= (((pair<K,V>*)right)->first))
            return 1;
        else 
            return -1;
    }

Then, inside some class I have vector of pairs class member:

vector<pair<K,V>> items;  

And some method for sort this vector by keys, using std::sort()

std::sort(items.begin(), items.end(), comparePairs<K,V>);

I have compilation errors within 

. What is a mistake?