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We recently described the synthesis of an unusual tricyclic system, whereby a cis-decalin was fused to a cis-hydrindane. Herein, we wish to describe the elaboration of this system towards steroid-like frameworks. This report describes how, en route to an attempted cardiotonic steroid synthesis, we stereoselectively functionalized the LHF-cyclohexyl ring with an ester ready for steroidal A-ring formation. Ultimately however, the required transposition of the cyclohexylketone did not occur as expected and resulted in the subsequent Robinson annulation forming an unusual steroidal constitutional isomerthe saturated cyclopenta[c]phenanthrene. Remarkably, such unusual tetracyclic connectivity has been reported just once in 70 years.

A highly enantioselective, organocatalytic, and scalable synthesis of a very unusual cis‐decalin‐cis‐hydrindane tricyclic diterpenoid system has been achieved. Despite the prevalent pharmacological space that the related trans,trans and trans,cis‐systems occupy, there have been no reports of an asymmetric synthesis of the cis,cis systems in the literature until now. We demonstrate the flexibility of our approach not only through access to a diverse range of products, all of which are attained in exceptionally high selectivities, but also by showing their easy conversion to the corresponding trans,cis‐system and other derivatives.

The synthesis of the novel 2',3'-cyclopropane nucleoside 3'-deoxy-3'-C-hydroxymethyl-2',3'-methylene-uridine is described. Stereoselective construction of the cyclopropane ring was achieved via Simmons-Smith cyclopropanation of a benzyl protected silyl enol ether, which was itself derived from 1,2-O-isopropylidene-α-D-xylofuranose.

Construction of protected 2,3-dideoxy-2-fluoro-2,3-endo-methylene-pentofuranoses from d-glyceraldehyde and 2,3-dideoxy-2-fluoro-3-C-hydroxymethyl-2,3-endo-methylene-pentofuranoses from d-isoascorbic acid, via Simmons-Smith-type stereoselective cyclopropanations on the respective fluoroallyl alcohols, is described. Synthesis of the corresponding conformationally locked sugar modified uridine and guanosine nucleosides was achieved via Vorbrüggen or Mitsunobu methodologies. Stereochemical confirmation of the novel nucleosides was performed on the basis of 2D NOESY NMR experiments. Analysis of 2',3'-dideoxy-2'-fluoro-3'-C-hydroxymethyl-2',3'-endo-methylene-uridine by X-ray crystallography yielded the principal conformational parameters and indicated that the furanoid ring adopted an (o)E/(o)T1, East pucker. The uridine and guanosine nucleosides were found to be inactive in the hepatitis C virus (HCV) cell-based replicon assay, which was corroborated on examination of the corresponding nucleoside triphosphates against the HCV NS5B polymerase.