Abstract: 21-norvitamin D.sub.3 analogs in which the methyl group normally attached to the side chain at carbon 20 has been replaced by a hydrogen atom. The compounds are characterized by a marked intestinal calcium transport activity while exhibiting much lower activity than 1.alpha.,25-dihydroxyvitamin D.sub.3 in their ability to mobilize calcium from bone. Because of their preferential calemic activity, these compounds would be useful for the treatment of diseases where bone formation is desired, such as osteodystrophy. Novel intermediates formed during the synthesis of the end products are also disclosed.

Abstract: Vitamin D.sub.3 analogs in which the methyl group normally attached to the side chain at carbon 20 has been exchanged with the hydrogen atom to form the 20-epi configuration. The compounds are characterized by a marked intestinal calcium transport activity while exhibiting much higher activity than 1.alpha.,25-dihydroxyvitamin D.sub.3 in their ability to mobilize calcium from bone. Because of their preferential calemic activity, these compounds would be useful for the treatment of diseases such as hypoparathyroidism or where bone formation is desired, such as low bone turn over osteoporosis. This disclosure is also directed toward 20-epi-3,5-cyclovitamin D compounds useful as intermediates in a process for preparing 20-epi-vitamin D.sub.3 analogs.

Abstract: The present invention is directed toward the use of 20-epi-vitamin D.sub.3 analogs to treat low bone turnover osteoporosis. The 20-epi compounds are characterized by a marked intestinal calcium transport activity while exhibiting much higher activity than 1.alpha.,25-dihydroxyvitamin D.sub.3 in their ability to mobilize calcium from bone.

Abstract: 21-norvitamin D.sub.3 analogs in which the methyl group normally attached to the side chain at carbon 20 has been replaced by a hydrogen atom. The compounds are characterized by a marked intestinal calcium transport activity while exhibiting much lower activity than 1.alpha.,25-dihydroxyvitamin D.sub.3 in their ability to mobilize calcium from bone. Because of their preferential calemic activity, these compounds would be useful for the treatment of diseases where bone formation is desired, such as osteodystrophy. Novel intermediates formed during the synthesis of the end products are also disclosed.

Abstract: The invention discloses a method for treating hypoparathyroidism with vitamin D.sub.3 analogs of the following formula: ##STR1## The methyl group in these compounds which is normally attached to the side chain at carbon 20 has been exchanged with the hydrogen atom attached to carbon 20 to form the 20-epi configuration. The compounds are useful for the treatment of hypoparathyroidism because of their high activity for mobilizing calcium form the bone.

Abstract: 21-norvitamin D.sub.3 analogs in which the methyl group normally attached to the side chain at carbon 20 has been replaced by a hydrogen atom. The compounds are characterized by a marked intestinal calcium transport activity while exhibiting much lower activity than 1.alpha.,25-dihydroxyvitamin D.sub.3 in their ability to mobilize calcium from bone. Because of their preferential calcemic activity, these compounds are useful for the treatment of diseases where bone formation is desired, such as osteodystrophy. Novel intermediates formed during the synthesis of the end products are also disclosed.

Abstract: A new method has been disclosed for obtaining derivatives of 4.beta.-/1'-alken-1'-yl/-2.xi.,5.dbd.-dihydroxy-3,3a.beta.,4,5,6,6a.beta.- hexahydro-2H-cyclopenta [b] furane useful in the synthesis of prostaglandins or their analogs, and a method for obtaining new sulphonyl initial compounds of the general formula 4, in which Z denotes a hydrogen atom or a protective group, Y denotes a group of the formula .dbd.CHOZ.sup.1, in which Z.sup.1 has the meaning stated for Z, whereby protective groups Z and Z.sup.1 may be the same or different, and Ar denotes optionally a substituted aryl group.In the method according to the invention the new sulphonyl derivative of the general formula 4 is alkylated with an electrophilic agent comprising: carbonyl derivatives, oxiranes and halohydrins or their derivatives; the alkylation product is transformed into derivatives of 4.beta.-/1'-alken-1'-yl/-2.xi.,5.alpha.-dihydroxy-3,3a.beta.,4,5,6,6a.beta .