Category:TP3
Contents |
Triterpene (C30) Classes
Ring configuration
The basic structure is 4 carbon rings, cyclopenta[a]phenanthrene, gonane, or sterane. The rings B/C are always trans in all natural steroids. If the rings C/D are trans, it is called gonane. If its stereochemistry is unspecified, it is called sterane. Most steroids take gonane form, but in cardenolides and bufanolides, the rings C/D are cis.
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| Cyclopenta[a]phenanthrene | Gonane |
The majority of steroids have methyl groups sticking out from the bridgehead positions C-10 and C-13. When these methyl groups (or hydrogens) stand above the plane, they are called β-configuration. Those below the plane are called α-configuration. If the configuration at any site is unknown, it is indicated as ξ (Greek Xi). By default, hydrogen atoms or substituents at the positions C-8, 9, 10, 13, and 14 are assumed to be 8β, 9α, 10β, 13β, and 14α configurations. C-5 is a special position, because there are as many 5α steroids as 5β are.
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| cholestane backbone | 5α-configuration | 5β-configuration |
Biosynthesis
The starting point is squalene, which is formed by joining two FPPs tail-to-tail. Bacterial cyclases use squalene directly, but those of the other species use 2,3-oxidosqualene for cyclization.
- In bacteria, squalene is cyclized via the 17α-deoxydammarenyl cation to hopene and other triterpenes[1].
- In eukaryotes, 2,3-oxidosqualene is cyclized via the protosteryl cation to lanosterol (animals and fungi) or cycloartenol (plants) by a series of 1,2-hydride and methyl shifts (Wagner-Meerwein shifts).[2]
- In plants, various triterpenes arise from the dammarenyl cation.
| BACTERIA | ANIMALS, FUNGI, and YEAST | PLANTS | |
| squalene | 2,3-oxidosqualene | ||
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squalene-hopene  cyclase[3]
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lanosterol  synthase
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lupeol  synthase
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17α-deoxydammarenyl cation[4]
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17β-protosteryl cation[5]
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17β-dammarenyl cation[6]
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| D-ring expansion[7]
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Wagner- Meerwein shift
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D-ring expansion
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lanosteryl cation
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baccarenyl cation
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hopene
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lanosterol
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lupeol
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- ↑ Bacterial squalene cyclases can accept oxidosqualene as their substrates, but oxidosqualene usually does not exist in bacteria
- ↑ A trace amount of phytosterols comes from lanosterol. Ohyama K, Suzuki M, Kikuchi J, Saito K, Muranaka T (2009) Dual biosynthetic pathways to phytosterol via cycloartenol and lanosterol in Arabidopsis Proc Natl Acad Sci USA 106(3):725-730
- ↑ The cyclization process is stepwise (not concerted). Squalene is not fully folded in the cyclase active site. Reinert DJ, Balliano G, Schulz GE (2004) Conversion of squalene to the pentacarbocyclic hopene. Chem Biol 11:121-6
- ↑ The C-17 chain of deoxydammarenyl cation is α-configuration. Wendt KU, Schulz GE, Corey EJ, Liu DR (2000) Enzyme mechanisms for polycyclic triterpene formation. Angew Chem, Int Ed 39:2812-33
- ↑ The C-17 chain of protosteryl cation is β-configuration, not α. Corey EJ, Virgil SC (1991) An experimental demonstration of the stereochemistry of enzymic cyclization of 2,3-oxidosqualene to the protosterol system, forerunner of lanosterol and cholesterol. J Am Chem Soc 113:4025-6
- ↑ The C-17 chain of dammarenyl cation is β-configuration. Xiong Q, Rocco F, Wilson WK, Xu R, Ceruti M, Matsuda SPT (2005) Structure and reactivity of the dammarenyl cation: configuration transmission in triterpene synthesis. J Org. Chem. 70:5362-75
- ↑ Ring C is also expanded from its 5-membered precursor.
Useful Reviews:
- Xu R, Fazio GC, Matsuda SPT (2004) On the origins of triterpenoid skeletal diversity. Phytochemstry 65:261-291 PMID 14751299
Design of Tri-terpene ID numbers ID番号の設計
12-DIGIT
| T | P | 3 | x | y | y | r | h | g | n | c | c |
- x ... species information
| Symbol at x | Kingdom | Phyla | Examples |
|---|---|---|---|
| I | Animalia | Arthropoda (Insects, crabs) | ecdysteroids |
| V | Chordate (Vertebrates) | sex steroids, corticosteroids, anabolic steroids | |
| O | Others | marine steroids | |
| P | Plantae | Phytosterols | lanosterols, cholesterols, brassinolides |
| S | Saponins | saponins | |
| F | Fungi | ergosterols | ergosterols |
| B | Bacteria | bacterial sterols | hopanoids |
- y ... backbone structure (母核構造)
| Symbol at y | Carbons | Steroids | Backbone Structure |
|---|---|---|---|
| GN | C17 | gonane |
|
| ES | C18 | estrane | 
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| AD | C19 | androstane | 
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| PG | C21 | pregnane | 
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| CA | C24 | cholane | 
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| CL | C27 | cholestane |
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| CM | C28 | campestane | 
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| EG | C28 | ergostane | 
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| SG | C29 (4 rings) | stigmastane | 
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| PR | C29 (4 rings) | poriferastane | 
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| Symbol at y | Carbons | Triterpenoids | Backbone Structure |
|---|---|---|---|
| PS | C30 | protostane | 
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| EU | C30 | euphane | 
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| LN | C30 | lanostane | 
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| CY | C30 | cycloartane | 
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| FS | C29 | fusidane | 
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| HP | C30 (5 rings) | hopane | 
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| FN | C30 (5 rings) | fernane | 
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| CC | C30 | cucurbitane | 
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| DM | C30 | dammarane | 
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| BC | C30 | baccharane | 
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| HL | C30 | holostane | 
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| PF | C29 (5 rings) | pfaffane | 
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| LP | C30 (5 rings) | lupane | 
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| OL | C30 (5 rings) | oleanane | 
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| FD | C30 (5 rings) | friedelane | 
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| TR | C30 (5 rings) | taraxastane | 
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| UR | C30 (5 rings) | ursane | 
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| SR | C30 (5 rings) | serratane | 
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- r ... number of major rings (環構造数)
Click above categories to see details.
- h ... hydroxylation pattern (水酸基数)
Click above categories to see details.
- g ... glycosylation pattern(糖修飾パターン)
Click above categories to see details.
- n ... number of sugars (修飾糖数)
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- c ... serial number (通し番号)
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