The document presents new synthetic approaches for cardiotonic steroids, which are an important class of bioactive natural products. Previous synthesis methods had limitations in modularity and accessibility of chemical space. The new approach uses a convergent Michael addition of functionalized donor and acceptor fragments to generate stereodiverse adducts. These adducts then undergo a double aldol reaction to form either the cis-α-C/D or cis-β-C/D steroidal ring system. Total syntheses of selected natural cardiotonic steroids were achieved to enable biological evaluation and exploration of structure-activity relationships.

1. 1
Presented by:-
M. Tech. (Pharm.) Sem. 1st
17PTPCM2717
DEPARTMENT OF PHARMACEUTICAL EDUCATION AND
RESEARCH (NIPER)
SECTOR- 67, S.A.S NAGAR, PUNJAB

2. Flow of presentation
Introduction
Cardiotonic Steroid’s
Previous synthetic approaches
New synthetic approaches
Total Synthesis and Biological evaluation of
Cardiotonic Steroids
Conclusion
2

3. Introduction
• Steroids are a structurally privileged class of bioactive natural products
found ubiquitously in nature
• These compounds are used naturally for a wide array of purposes
including hormonal/cell signaling, lipid membrane stability, and
defense mechanisms
• These steroidal core has treated human ailments such as cancer, heart
failure, inflammation, allergies, metabolic diseases, and other health
related areas like contraception and physical fitness
3
Biochemistry 6th Edition; 2016

4. Cont..
4
Biochm. Mol. Biol. Educ. 2008, 36, 244–248
Biochem. Mol. Biol. Educ. 2008, 36, 244–248

5. Cardiotonic Steroids
• Cardiotonic steroid mainly represent a important steroidal class which
consist a basic ring name is Cyclopentano- perhydro phenanthrine
β- face
α- face
5
Chemistry - A European Journal. 2012, 3092–3120.

6. Cont..
Natural sources
Chemical sources
Heart failure and cardenolide MOA
Binding mode of cardenolides
Reported activity of cardiotonic steroids
6

7. Natural source
• It was first reported in 1542, when the German physician and
professor of botany Leonard Fuchs compiled a herbarium of all plants
known at the time. He gave the plant its name (from digitulus meaning a
“small finger”)
• The most well-known plant containing cardiac steroids is the foxglove
• There are two type of natural source –
 Animal source
 Plant source
7
Molecules. 2000, 51–81

8. Cont..
1. Animal sources:-
8
Chem. - A Eur. J. 2012, 18, 3092 – 3120.

9. Cont..
2. Plant soureces :-
9
Chem. - A Eur. J. 2012, 18, 3092 – 3120.

10. Chemical source
10
Naunyn. Schmiedebergs. Arch. Pharmacol. 1985, 329 , 414–426

11. Heart failure and cardenolide MOA
Cardenolides act on the heart by binding and inhibiting the catalytic α-subunit
(isoforms α1, α2, α3, and α4) of the Na+/K+-ATPase pumps found on the
surface of cardiac myocytes
11

12. Binding mode of cardenolides
X-ray crystallographic analysis of Na+/K+-ATPase–cardenolide binding has
been achieved and revealed valuable insights into the nature of the binding
interactions involved. In one case, pig kidney Na+/K+-ATPase (α1 isoform)
was complexed with ouabain and the x-ray was resolved to 3.4 Å resolution.
12
Proc. Natl. Acad. Sci. 2013, 110 , 10958–10963.

13. Reported activity of cardiotonic steroids
CANCER TYPE COMPOUNDS CELL TYPE
Breast digitoxin, digoxin, proscillaridin A,
Oubain, digoxigenin, gitoxin,
gitoxigenin
MCF-7, MDA-MD-435
Prostate Oleandrin, oubain, digoxin, bufalin,
cinobufagenin
PC-3, LNCaP, DU145
Melanoma Digoxin, oleandrin, digitoxin,
proscillaridin A, oaubain, digitonin
UACC-62, BRO
13

14. Cont..
Lung Digitoxin, digoxin, oaubain,
unbs1450, oleandrin
A-549, NCI-H-398, Calu 1,
sklu 1, NCI-H6, H69AR
Leukemia Bufalin, oleandrin, digitoxin,
proscillaridin A, ouabain
HL60, U937, CCRF-CEM,
CEM-VM-1
Neuroblastoma
Digoxin, ouabain SH-SY5Y, Neuro-2a
Renal Digitoxin, digoxin, digitoxigenin,
proscillaridin A, ouabain
TK-10, ACHN
Myeloma
Digitoxin, digoxin, proscillaridin a,
digitoxigenin, ouabain, digitonin,
lanatocide C
8226-S, 8226-LR5, 8226-
DOX-40
Pancreatic Oleandrin PANC-1
14Nat Rev Drug Discov 2008, 7, 926–935.

15. Previous synthetic approaches
Bachmann’s synthesis of Equillin.
Daniewski and co-workers reported the
first synthesis cardenolide core.
First total synthesis of a natural
cardenolide
Deslongchamp’s synthesis of ouabain
15

16. Cont..
Bachmann’s synthesis of Equillin :-.
16
J. Am. Chem. Soc. 1940, 62 , 824–839

17. Cont..
Deslongchamp’s synthesis of ouabain :-
Preliminary Studies on a Michael/Aldol Cascade
17
Chem. - An Asian J. 2009, 4 , 725–741

18. Cont..
Glycosylation of Ouabagenin to Ouabain
18
Org. Lett. 2002, 4 , 4693–4696.

19. New synthetic approaches
1. Rationale for new synthetic approach :-
• One of the main hurdles associated with these approaches is modularity; and the
design of more drug-oriented approaches remains a formidable challenge.
• When a synthetic route is conceived specifically to access a single complex target, it
is often not amenable to diversification and the accessible chemical space
surrounding the target is limited.
• For the purpose of exploring new therapeutic agents, it is highly desirable that a
methodological approach features access to an entire class of natural products.
• In this regard, modularity and plasticity should be ingrained in the synthetic
foundation of the approach. Designing such a method requires a convergent
technique
2. Methodological design overview :-
19
Molecules. 2000, 51–81

20. Cont..
3. Michael donor fragment design :-
4. Michael acceptor fragment design :-
20

21. Cont..
5. Cyclization of michael adducts into steroidal cores :-
6. Origin of stereodivergent cyclization results :-
Two-step Cyclization Approach to cis-β-C/D Steroidal Core.
21

22. Cont..
Suggested Pathways for Diastereoselective Michael Adduct Cyclization
22

23. Cont..
Synthesis of cis-β-C/D Steroidal Cores Via Two-step Protocol
23
J. Am. Chem. Soc. 2015, 137 , 14341–14348

24. Total synthesis and biological evaluation
24
Angew. Chemie - Int. Ed. 2013, 52 , 5300–5304.

25. Cont..
Retrosynthesis of Selected Targets via Key Intermiate
25
J. Am. Chem. Soc. 2015, 137 , 14341–14348.

26. Conclusion
26
•A variety of uniquely structured β-ketoesters and 2-substituted enones could
be successfully coupled under these conditions. This allowed the synthesis
of a library of Michael adducts in excellent selectivity
•At this stage cyclization studies were undertaken to affect a double aldol
reaction and complete the steroidal nucleus
•They discovered stereo divergent conditions for producing the steroidal
cores. Depending on the conditions used, produces cis-α-C/D or cis-β-C/D
ring junctions.
J. Am. Chem. Soc. 2015, 137 , 14341–14348.

27. Cont..
27
Summary of Stereo divergent Cyclization Results

28. Cont…
28
Target and Required Modification :-

29. Structure activity relationship (SAR)
29