This invention provides a novel class of vitamin D related compounds,
namely, the 2-alkylidene-19-nor-vitamin D derivatives, as well as a
general method for their chemical synthesis. The compounds have the
formula: ##STR00001## where Y.sub.1 and Y.sub.2, which may be the same
or different, are each selected from the group consisting of hydrogen and
a hydroxy-protecting group, R.sub.6 and R.sub.8, which may be the same or
different, are each selected from hydrogen, alkyl, hydroxyalkyl and
fluoroalkyl, or when taken together represent the group
--(CH.sub.2).sub.x-- where x is an integer from 2 to 5, and where the
group R represents any of the typical side chains known for vitamin D
type compounds. These 2-substituted compounds are characterized by
relatively high intestinal calcium transport activity and relatively high
bone calcium mobilization activity resulting in novel therapeutic agents
for the treatment of diseases where bone formation is desired,
particularly low bone turnover osteoporosis. These compounds also exhibit
pronounced activity in arresting the proliferation of undifferentiated
cells and inducing their differentiation to the monocyte thus evidencing
use as anti-cancer agents and for the treatment of diseases such as
psoriasis.