typedef union{
unsigned char str[5];
unsigned long lon;
}uni;
uni my = {"1234"};
int main()
{
printf("0x%08lx\n",my.lon);  // 0x34333231
// А вот по-Вашему:
printf("0x%08lx\n", *((unsigned long*)("1234")) ); //0x34333231	
return 0;
}