A novel synthetic approach to (20R)- and (20S)-21-hydroxy steroids. Synthesis of a marine sterol 21-hydroxycholesterol.

A short and efficient synthesis of steroid synthons, di(tert-butyldimethylsilyl) ethers of 3,21-dihydroxy-24-nor-chol-5-en-23-al (8 and 10) and of ethyl 3,21-dihydroxy-25-homo-chola-5,23-dien-25-oate (9 and 11), having natural (20R) and unnatural (20S) configuration from 3β-(tert-butyldimethylsilyloxy)-14α,20ξ-card-5-enolide (2) is reported. Further elongation of the side chain of these synthons provides a new method for the synthesis of (20R) and (20S)-21-hydroxy steroids. The utility of the method was exemplified by the synthesis of a natural marine sterol - 21-hydroxycholesterol (18).

Two isomeric cucurbitane derivatives.

Two isomeric cucurbitane derivatives, 3beta,7alpha,11beta-triacetoxycucurbit-5(10)-ene, (I), and 3beta,7alpha,11beta-triacetoxy-5alpha-cucurbit-1(10)-ene, (II), both C(36)H(58)O(6), have their single endocyclic C=C double bonds in different positions. This results in differences in the conformation of the four-ring system, which is close to a half-chair/half-chair/chair/half-chair arrangement in (I) and to a half-chair/twist-boat/boat/half-chair arrangement in (II). The orientation of some of the substituents is also different; the 3beta-acetoxy group is in an equatorial position in (I) but in an axial position in (II), while the 11beta-acetoxy group occupies an axial position in (I) and an equatorial position in (II).

Synthesis and structural characteristics of lithocholate triads: steroid-type channels occupied by spacer fragments.

Reported in this paper are the syntheses and X-ray investigations of C(2) symmetrical molecular A-B-A triads consisting of two steroid units (lithocholic acid or its methyl ester) joined together by linkers derived from bifunctional molecules such as terephthalic acid or N,N'-dicarboxypiperazine. Unlike their monomeric analogues, some of these compounds form inclusion complexes. All steroidal triads form crystals that are highly pseudo-centrosymmetric, in which the constituting molecules are held together either exclusively by van der Waals forces or form lattice inclusion complexes, with guest molecules hydrogen bonded to the host.

The alpha- and beta-epoxides of 3beta-acetoxy-5alpha-lanost-9(11)-en-7-one.

The structures of 3beta-acetoxy-9alpha,11alpha-epoxy-5alpha-lanost-9(11)-en-7-one and 3beta-acetoxy-9beta,11beta-epoxy-5alpha-lanost-9(11)-en-7-one, C(32)H(52)O(4), differ in their respective substituted cyclohexanone rings but adopt similar conformations in the other three rings. In both of the crystal structures, weak intermolecular C-H..