Contemporary Synthetic Strategies towards Secosteroids, abeo-Steroids, and Related Triterpenes

Abstract

Steroids have long been sought after as synthetic targets. Their rearranged counterparts, though, have only recently received more attention, when isolation and biological testing programs revealed several molecular entities that were both structurally intriguing as well as biologically relevant. This review will highlight contemporary synthetic approaches towards the growing class of seco- and abeo-steroids and some related triterpenoid natural products.1 Introduction2 Cyclocitrinol2.1 Li’s Synthesis of Cyclocitrinol2.2 Gui’s Synthesis of Cyclocitrinol3 Strophasterol3.1 Heretsch’s Synthesis of Strophasterol A3.2 Kuwahara’s Synthesis of Strophasterols A and B4 Pleurocin A/Matsutakone and Pleurocin B4.1 Heretsch’s Synthesis of Pleurocin A/Matsutakone and Pleurocin B5 Aplysiasecosterol A5.1 Li’s Synthesis of Aplysiasecosterol A6 Glaucogenins C and D6.1 Tian’s Syntheses of 5,6-Dihydro-glaucogenin C and Glaucogenin D7 Physalin B7.1 Sodeoka’s Synthesis of the DFGH Ring System of Physalin B8 Limonin8.1 Hirama’s Synthesis of (±)-Limonin9 Schiglautone A9.1 Ding’s Synthesis of (±)-atrop-Schiglautone A10 Conclusion

Designed whole-cell-catalysis-assisted synthesis of 9,11-secosterols

“…Various enzymatic or semisynthetic methods have also been exploited in the synthesis of steroids [2][3][4]. A more challenging synthesis of secosteroids with unique broken tetracyclic carbon skeletons and abeo-steroids with migrated bonds has received attention only recently [5,6]. As the bond cleavage may occur at the 5,6-, 9,11-, 9,10-, 8,9-, 8,14-or 13,17-positions (Figure 1A), the selection of synthetic methods for secosteroids is wide.…”

Synthesis of Degraded Limonoid Analogs as New Antibacterial Scaffolds against Staphylococcus aureus

“…With this aim, the range of drug-like parameters according to 11 molecular properties were studied (Table 1). Unfortunately, the availability of limonoids from natural sources is limited and their total syntheses are a challenge because they usually require a considerable number of reaction steps [16,17].…”

“…Unfortunately, the availability of limonoids from natural sources is limited and their total syntheses are a challenge because they usually require a considerable number of reaction steps [ 16 , 17 ].…”

“…In literature, two limonoids are described to exhibit multiple-drug resistance activity against eight MDR bacterial strains including S. aureus strains (Figure 1, swietenolide and 2-hydroxy-3-O-tigloylswietenolide) [15]. Unfortunately, the availability of limonoids from natural sources is limited and their total syntheses are a challenge because they usually require a considerable number of reaction steps [16,17].…”

Asymmetric Total Synthesis of Phomarol

“…Because of their important bioactivity and diverse structures, steroids play an important role in organic synthesis and drug discovery. [1][2][3][4][5][6][7][8] Phomarol (1) (Figure 1), a C25 steroid with an unusual architecture, was isolated by Jung and co-workers 9 in 2016 from a jellyfish-derived fungus. Structurally, phomarol (1) contains a sterically compact [7-6-6-5-6]-fused pentacyclic framework, with a highly functionalized tetrahydropyran E-ring (highlighted in blue).…”