The Total Synthesis of Chalcitrin. Biological & Biomedical Sciences Coursework
The Total Synthesis of Chalcitrin- writing up the Scheme 6 and conclusion part
Scheme 5 , Scheme 6 and Conclusion (4 pages)
The attachments I uploaded have group member’s part involved. You can refer to it. We are focusing on the nature of mechanism. Scheme 5: Second and third coupling attempts [4 steps]
Tandem stille reactions used as planned
2nd attempt - Bistannane tricyclic intermediate + halide pulvinic acid = no product
Switch the partners; have the tricyclic be the halide partner. This is the flexibility of the reaction proving to be advantageous 3rd attempt - Double halide tricyclic intermediate + stannane pulvinic acid = product
Scheme 6: Preparing stannane pulvinic acid [6 Steps]
Stannane group cannot be directly added/substituted to pulvinic acid commercial sourceTherefore the group had to synthesise the stannane pulvinic acid from scratch (tetronic acid)Conclusion: Overall yield, total steps
Summarise and highlight some key reactions?Interesting bits:
In the end, the longest route (everything made from scratch) was the only successful path to product reported
The flexibility of switching the possible coupling partners contributed to the success of the total synthesis
Characterisation after product synthesis confirmed that natural isolate exists in carboxylate form, not the protonated form which was initially synthesised
These two mechanisms must involve.
Make the references clear, thanks.
If use images from paper, please also cite those.
Do not write the formula in the article, please.
J. Am. Chem. Soc. 2019, 141, 4515−4520
Assessment will be based on:
● the retrosynthesis
● the understanding of the details of the chemistry involved
● its organisation into a coherent form
● the clarity of review
● critique and discussion of the key steps and strategy in the synthesis
The aim is to discuss the critical features of the synthesis; the focus should be:
● the nature (mechanism, i.e. arrow-pushing!) of key C-C bond forming steps
● overall strategy
● stereocontrol
● and any other novel/interesting components of the published work.
Detailed chemistry of protection-deprotection sequences and redox chemistry need not be emphasised, but may be necessary in some cases
Plan for review -- breakdown each scheme and analyse the chemistry for each step
Intro -- Patrick
● Source of Chalcitrin
● Pulvinic acid dimers (analogues of Chalcitrin)
● Interest area of group
● Overview of dimer scaffold
Scheme 1: Retrosynthesis [8 steps]
● Show general reaction for coupling reaction (heck/stille) with possibilities of switching between the halide and metal partners -- shows great flexibility of the synthesis
Scheme 2: Formation of tricyclic intermediate [10 steps]
● Preparing the tricyclic intermediate to be the metal (tin) coupling partnerScheme 3: First coupling attempt [6 steps]
● Stille and heck reactions coupled with pulvinic acid as the halide partner because this is the faster route (cannot directly convert pulvinic acid to stannane)
● Stille was determined to be the only successful coupling reaction, so now the target is to have tandem (2x) stille reaction instead of Stille+Heck
● This requires preparing a double vinyl halide intermediate for subsequent conversion to bistannane tricyclic partnerScheme 4: Preparing double vinyl halide intermediate [8 steps] Scheme 5: Second and third coupling attempts [4 steps]● Tandem stille reactions used as planned
● 2nd attempt - Bistannane tricyclic intermediate + halide pulvinic acid = no product
● Switch the partners; have the tricyclic be the halide partner. This is the flexibility of the reaction proving to be advantageous
● 3rd attempt - Double halide tricyclic intermediate + stannane pulvinic acid = productScheme 6: Preparing stannane pulvinic acid [6 Steps]
Stannane group cannot be directly added/substituted to pulvinic acid commercial source● Therefore the group had to synthesise the stannane pulvinic acid from scratch (tetronic acid)Conclusion
● Overall yield, total steps
● Summarise and highlight some key reactions?
● Interesting bits:
○ In the end, the longest route (everything made from scratch) was the only successful path to product reported○ The flexibility of switching the possible coupling partn...
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