both compounds ( 4a and 6a ) were about 2 times as active as 25- ( oh ) d3 endoperoxides ( 2a and 3a ) and about 7 times as active as 25-hydroxyvitamin d3 ( 1a ) in inducing differentiation of hl-60 cells .
C2713074
25
C0006657
25-hydroxyvitamin d3