SugarSync API get user's info: Error 401 unauthorized - api

Question

I'm trying to get a request for the user's information using WinHttp functions. The REST API call for SugarSync is referenced here.
My code is as follows:
DWORD dwBytesWritten = 0;
DWORD dwStatusCode = 0;
DWORD dwSize = sizeof(DWORD);
BOOL bResults = FALSE;
string data;
HINTERNET hSession = NULL,
hConnect = NULL,
hRequest = NULL;
WINHTTP_PROXY_INFO proxyInfo;
winhttpintObj.setProxyInfo(proxyInfo);
HINTERNET hSession = WinHttpOpen( L"A WinHTTP Example Program/1.0",
WINHTTP_ACCESS_TYPE_DEFAULT_PROXY,
WINHTTP_NO_PROXY_NAME,
WINHTTP_NO_PROXY_BYPASS, 0);
HINTERNET hConnect = WinHttpConnect( hSession, L"api.sugarsync.com",
INTERNET_DEFAULT_HTTPS_PORT, 0);
HINTERNET hRequest = WinHttpOpenRequest( hConnect,
L"GET", L"/user/<userID>",
NULL,
WINHTTP_NO_REFERER,
0,
WINHTTP_FLAG_SECURE);
string header("Authorization: ");
header += (accessToken);
header += "\n";
wstring ws = wstring(header.begin(), header.end());
WinHttpAddRequestHeaders( hRequest, ws.c_str(), (ULONG)-1L, WINHTTP_ADDREQ_FLAG_ADD );
WinHttpSendRequest( hRequest,
WINHTTP_NO_ADDITIONAL_HEADERS,
0,
WINHTTP_NO_REQUEST_DATA,
0,
0,
0 );
WinHttpReceiveResponse( hRequest, NULL);
WinHttpQueryHeaders( hRequest,
WINHTTP_QUERY_STATUS_CODE |
WINHTTP_QUERY_FLAG_NUMBER,
NULL,
&dwStatusCode,
&dwSize,
NULL );
cout << "dwStatusCode: " << dwStatusCode << endl;
The accessToken is https://api.sugarsync.com/authorization/....... The status code returned is 401: Authorization required. However, I've already specified it in the header. May I know where has the problem occurred and what is the possible way to resolve it? Thank you.