Total Synthesis of Mucronin B

Abstract

The intramolecular carbonylation of a carbyne-metal fragment outlined in Scheme (2) is in our opinion of significance in connection with the homogeneously and heterogeneously catalyzed reduction of CO with H217a*b1, even though there is so far evidence in only one case for the existence of M=CR units as primary essential species for the carbon-carbon coupling in the Fischer-Tropsch synthe-s~s"'~. The ketenyl derivatives synthesized from such species by CO addition possibly occur, inter a h , as intermediates during formation of oxygen-containing organic compounds. Moreover, reaction (2) shows that the CR part of a metal-bonded ylide moiety R,P=C-is synthetically available and behaves like a carbyne ligandfS1.

Total Synthesis of Mauritines A, B, C, and F: Cyclopeptide Alkaloids with a 14‐Membered Paracyclophane Unit

“…A major contribution to this field came from Schmidt and co‐workers,7 who developed a particularly efficient carboxylic acid activation method (through a pentafluorophenyl ester) for conducting the key macrolactamization step. On the basis of this methodology, they achieved the total syntheses of zizyphine A ( 4 )7c,e and mucronine B at the beginning of the 1980s,7f,g followed in 1991 by the 14‐membered cyclopeptide alkaloid frangulanine 7h. This activation methodology was also featured in the total syntheses of nummularine F,8b,c sanjoinine G1,8f, 10a and frangufoline8h by the groups of Joullié and Han.…”

A General Route to Cyclopeptide Alkaloids: Total Syntheses and Biological Evaluation of Paliurines E and F, Ziziphines N and Q, Abyssenine A, Mucronine E, and Analogues

“…Their structures are slightly different from those of their 13‐membered ring homologues because they incorporate a methylene group in place of the ether bond and possess three amino acids within the macrocycle. Whereas much work has been devoted to the synthesis of the 13‐ or 14‐membered ring cyclopeptide alkaloids,9–15 a single synthesis of a 15‐membered ring compound, mucronine B,10b,10c featuring a macrolactamization reaction and a stepwise installation of the enamide, had been reported 34. We therefore initiated studies directed towards the extension of our synthetic route to the preparation of this subclass of cyclopeptide alkaloids and chose abyssenine A6c,35 ( 3 ) and mucronine E6c ( 48 ) as target molecules (Scheme ).…”

Biomimetic Synthesis of Azole‐ and Aryl‐Peptide Alkaloids

“…Ring closure as the key step in each of these synthetic routes has been accomplished at different positions of the molecular scaffold (Figure 9.9) [61]. Schmidt et al have introduced a macrolactamization approach based on the activation of a carboxyl-group as a pentafluorophenyl ester, which was further applied to the synthesis of several cyclopeptide alkaloids (Schmidt et al [62][63][64][65][66][67][68][69], Joullié et al [70][71][72][73][74][75][76], Han et al [77][78][79]). …”

“…The simplest ones are cyclic tripeptides containing isodityrosine 60 as a common element (Figure 9.10). Biosynthetically, they are derived from oxidative cyclization of a terminal tyrosine, either at the C-terminus (61) or at the N-terminus (62)(63)(64)(65)(66)(67)(68)(69)(70). These different biphenyl-ether linkages lead to diverse biological activities of otherwise related structures.…”

“…While K-13 (61), isolated from Micromonospora halophytica [87] acts as a potent angiotensin I converting enzyme (ACE) inhibitor, its inhibition of aminopeptidase B is very weak [88]. compound class on the other hand (63)(64)(65)(66), produced by Penicillium rugulosum, shows potent inhibition of aminopeptidase B [89]. Bouvardin (71) was first isolated from Bouvardia ternifolia (Rubiaceae) and features an 18-membered peptide ring next to the cycloisodityrosine unit (Figure 9.10) [90].…”