Try this

declare @s-2 varchar(8000) ='SENT REQUEST TO BREC TO VALADATE. WHY OOA LETTER WAS SENT. PER'

select stuff(

(select '.'+upper(left(item,cappos))+lower(substring(item,cappos+1,8000))

from(

select *, cappos= patindex('%[^ ]%',item)

from DelimitedSplit8K(@s,'.')

) t

order by ItemNumber

for xml path('') )

,1,1,'')

Find DelimitedSplit8K code here http://www.sqlservercentral.com/articles/72993/