Synthesis of (−)-Calicoferol B

Abstract

The first total synthesis of (-)-calicoferol B (III) is described. The cyclozirconation product I, prepared in enantiomerically pure form, was converted into the CD ring chiron II. This was coupled with the aromatic A-ring, and then the side chain was constructed with control of relative and absolute configuration to complete the total synthesis of III. The first total synthesis of (-)-calicoferol B (1) is described. The cyclozirconation product 8, prepared in enantiomerically pure form, was converted into the CD ring chiron 6. This was coupled with the aromatic A-ring, and then the side chain was constructed with control of relative and absolute configuration to complete the total synthesis of 1.

Total Synthesis of Fawcettimine-Type Alkaloid, Lycojaponicumin A

“…Therefore, Z- 14 should be preferentially transformed to E- 14 . However, this transformation turned out to be quite challenging under common isomerization conditions . After an extensive investigation, pleasingly, it was found Z- 14 could be completely converted into E- 14 via a photoinduced isomerization with an LED lamp (395 nm, 50 W) in nearly quantitative yield .…”

Synthetic Studies on Selective, Proapoptotic Isomalabaricane Triterpenoids Aided by Computational Techniques

“…As we expected, enolization of the ketone on the desired sidetoward the quaternary centerwas highly disfavored over enolization to the other side, and none of the desired constitutional isomer could be detected after model aldol reactions. Overcoming selectivity issues of this nature by screening bases and reaction conditions is quite rare, and generally, one must resort to blocking the undesired position with a removable group. Including the reductive transposition, this strategy would require, at a minimum, five steps to accomplish only two meaningful transformations, namely, reduction of enone 30 and the attachment of the pendent acetyl group.…”

Synthesis of (−)-astrogorgiadiol

“…3 Remarkably, while the active metabolite of Vitamin D, 1α,25-dihydroxy vitamin D 3 (calcitriol) 1 upregulates the cytokine osteopontin (OPN) in cell culture, 30 nM 2 downregulates OPN. 3 This is the first small molecule known to downregulate this cytokine.…”

“…3 Remarkably, while the active metabolite of Vitamin D, 1α,25-dihydroxy vitamin D 3 (calcitriol) 1 upregulates the cytokine osteopontin (OPN) in cell culture, 30 nM 2 downregulates OPN. 3 This is the first small molecule known to downregulate this cytokine. Osteopontin has been shown to play a significant role in the development of virulent asthma, 4 and OPN knockout mice do not develop osteoporosis.…”