Add-Type -AssemblyName  System.DirectoryServices.AccountManagement
$ctype = [System.DirectoryServices.AccountManagement.ContextType]::Domain
$SSL = [System.DirectoryServices.AccountManagement.ContextOptions]::Negotiate -bor [System.DirectoryServices.AccountManagement.ContextOptions]::SecureSocketLayer
$ContextType = New-Object -TypeName System.DirectoryServices.AccountManagement.PrincipalContext –ArgumentList $ctype,"<domain name>",”<container>”,$SSL
$group = [System.DirectoryServices.AccountManagement.GroupPrincipal]::FindByIdentity($ContextType ,"<ad sync source group>")
$group.GetMembers($true) | select GivenName, UserPrincipalName | Export-Csv -Path C:\TEMP\fb_users.csv