Splitting of β-carotene in the sexual interaction of Phycomyces
作者:Silvia Polaino、M. Mar Herrador、Enrique Cerdá-Olmedo、Alejandro F. Barrero
DOI:10.1039/c0ob00321b
日期:——
Two new 7-carbon compounds, 1 and 2, have been found in the culture medium of Phycomyces blakesleeanus. A genetic test showed that they derive from β-carotene. These new molecules represent the missing link that proves that β-carotene is split into fragments of 18, 15 and 7 carbon fragments, each head of a separate family of apocarotenoids.
Application of Chiral Cationic Catalysts to Several Classical Syntheses of Racemic Natural Products Transforms Them into Highly Enantioselective Pathways
作者:Qi-Ying Hu、Gang Zhou、E. J. Corey
DOI:10.1021/ja046154m
日期:2004.10.1
This paper describes the application of chiral oxazaborolidinium cations of type 2 to various enantioselective Diels-Alder reactions that have served as early key steps for the syntheses of complex natural products. In the original syntheses these Diels-Alder reactions produced racemic adducts and led to racemic target molecules unless a separation of enantiomers by classical resolution was employed. By use of chiral catalysts of type 2, chiral products were obtained directly from Diels-Alder reactions of achiral components in excellent yield and enantioselectivity and with the mechanistically predicted absolute configuration. As a result, a number of classical syntheses could be converted to enantioselective versions, including (1) cortisone/cortisol (Merck/Sarett), (2) dendrobine (Kende), (3) vitamin B-12 (Eschenmoser), (4) myrocin C (Chu-Moyer/Danishefsky), (5) coriolin and hirsutene (Mehta), (6) dendrobatid 251F (Aube), (7) silphinene (Ito), and (8) nicandrenone core (Stoltz/Corey).
Enantioselective Total Synthesis of (-)-7-Deacetoxyalcyonin Acetate. First Synthesis of a Eunicellin Diterpene
作者:David W. C. MacMillan、Larry E. Overman
DOI:10.1021/ja00146a028
日期:1995.10
A General Strategy for the Synthesis of Cladiellin Diterpenes: Enantioselective Total Syntheses of 6-Acetoxycladiell-7(16),11-dien-3-ol (Deacetoxyalcyonin Acetate), Cladiell-11-ene-3,6,7-triol, Sclerophytin A, and the Initially Purported Structure of Sclerophytin A
作者:David W. C. MacMillan、Larry E. Overman、Lewis D. Pennington
DOI:10.1021/ja016351a
日期:2001.9.1
step; chemo- and stereoselective hydroxyl-directed epoxidation of 49, 72, and 90 followed by regioselective reductive opening with hydride to install the C3 tertiary hydroxylgroup; and a diastereoselective Nozaki-Hiyama-Kishi cyclization of iodoaldehyde 56 to forge the oxacyclononane ring and the C6 hydroxyl stereocenter. Other key transformations include chemo- and stereoselective hydroxyl-directed