Hi Raju,
Assuming you want accrued interest posting.
This can be achieved through update type SE8701 - Accrued interest pay and SE8702 - Accrued interest receive. Select effective interest calculation check box in update type then you can post accrued interest for purchase and sale transaction.
Update Type - SE8702
Update Type SE8701
Purchase transaction
you can select with or without accrued interest calculation for purchase and sale transaction same way.
For this requirement key date valuation is not required. hope this will solve your issue.