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Synthesis of porphobilinogen and studies on the synthesis of cobyric acid.

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Call No.	QD400.5.S95 L5 2002
Author	Li, YongKai
Title	Synthesis of porphobilinogen and studies on the synthesis of cobyric acid.
Date	2002
Abstract	This thesis describes the synthetic study of two biologically related natural products: porphobilinogen (PBG) and cobyric acid. PBG is the key intermediate in the biosynthesis of all naturally occurring tetrapyrrolic 'pigments of life', including heme, chlorophylls and vitamin B12. Previous chemical syntheses of PBG involve lengthy steps, toxic reagents and low yields. The current market price for this simple monopyrrole is about $10,000 per gram. Due to its possible applications in tumor photodynamic therapy, an efficient synthesis of PBG is highly desirable. Our synthesis starts from furfurylamine, which is commercially available in large quantities. The key reactions are: (1) Johnson-Claisen enol-ester rearrangement of the allylic alcohol intermediate followed by intramolecular Diels-Alder cyclization (IMDA) in one pot; (2) Ozonolysis of the bridged alkene intermediate followed by oxidative fragmentation of the resulting ozonide. This approach takes 7 linear steps with 20% overall yield, which is by far the most practical and efficient. During the course of this study we also explored the acceleration effect of steric hindrance on the IMDA reaction. Cobyric acid is the tetrapyrrolic core of vitamin B12 and coenzyme B12, which are important cofactors in fundamental metabolism. It can be viewed as a derivative of the hypothetical corrin nucleus with seven stereogenic centers on the macrocycle. Vitamin B12 was first synthesized by the joint efforts of Woodward and Eschenmoser. In the past our group has successfully introduced the meso -methyl groups and iteratively coupled the individual rings in the model study. The second part of this thesis describes our general strategy toward enantioselective syntheses of individual ring precursors of cobyric acid. Synthesis of the C-ring fragment was achieved in high enantioselectivity, by employing a key 'reagent controlled' Ireland-Claisen rearrangement followed by palladium-catalyzed oxidative lactonization. In addition, we have also developed a short synthesis of racemic C-ring fragment utilizing a classic Ireland-Claisen arrangement.
Description	1 online resource (v, 217 leaves) : illustrations
Format	application/pdf
Advisor	Jacobi, Peter A.
Subject	Tetrapyrroles -- Synthesis. ; Porphyrins -- Synthesis. ; Vitamin B12 -- Synthesis.
College	Dartmouth College -- Department of Chemistry.
Issuing Body	Dartmouth Dissertations are made available through the Dartmouth Digital Library.
Degree	Thesis (Ph.D)--Dartmouth College.
Copyright	In Copyright. This material is protected by copyright and/or related rights. You are free to use this material in any way that is permitted by copyright law that applies to your use. For other uses, you need to obtain permission from the rights-holder(s). http://rightsstatements.org/page/InC/1.0/
DOI	https://doi.org/10.1349/ddlp.2796

Title	li2002 1
Full Text	Structural and Functional Studies o f Core-Binding Factors (CBFs) A Thesis Submitted to the Faculty in partial fulfillment of the requirements for the The Department of Biochemistry by Zhe Li DARTMOUTH COLLEGE Hanover, New Hampshire December, 2002 degree of Doctor of Philosophy in Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.

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Synthesis of porphobilinogen and studies on the synthesis of cobyric acid.

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