Hi momowin,
Do you mean Office 365 Enterprise K1 plan?
According to Office 365 service description, Directory Sync tool and single sign-on (SSO) are supported in Office 365 Enterprise K1 plan.
Office 365 Platform Service Description: technet.microsoft.com/.../office-365-platform-service-description.aspx
You can search for the key word “Directory” and “single sign-on” within the service description article:
Thanks,
Young Yang