Divergent Synthesis of Revised Apratoxin E, 30-epi-Apratoxin E, and 30S/30R-Oxoapratoxin E

Abstract

In this report, originally proposed apratoxin E (30S-7), revised apratoxin E (30R-7), and (30S)/(30R)-oxoapratoxin E (30S)-38/(30R)-38 were efficiently prepared by two synthetic methods. The chiral lactone 10, recycled from the degradation of saponin glycosides, was utilized to prepare the key nonpeptide fragment 9. Our alternative convergent assembly strategy was applied to the divergent synthesis of revised apratoxin E and its three analogues. Moreover, ring-closing metathesis (RCM) was for the first time found to be an efficient strategy for the macrocyclization of apratoxins.

Synthesis of the Sex Pheromone of the Tea Tussock Moth Based on a Resource Chemistry Strategy

“…In practice it proved laborious to purify the very polar hydroxyacid, so it was used directly without further purification. To reduce the carboxylic acid effectively, the ethyl ester 5 could be obtained in 75% yield for two steps under acid-catalyzed esterification conditions [11], but according to the 1 H-NMR and 13 C-NMR spectra (supplementary material), it could be observed that the hydroxyl group in the 2-position was partially epimerized. We suspect this resulted from the basic conditions used.…”

“…Several preparation methods of compound 7 that can be found in the literature. Aside from Wei’s route [11], the rest require more chemical operations [16], an expensive chiral auxiliary such as the Evans template [17,18,19] or poisonous cyanide [20]. The e.e.…”

“…If a new H 2 O 2 oxidation procedure were to be applied to pregna-16,20-diol, a large quantity of (5 S )-3-hydroxy-5-methyltetrahydro-2 H -pyran-2-one ( 2 ) could become available, and 1000 tons of chiral material could be recycled. Tian et al developed a toolkit of chiral building blocks from this resource chemical [10] and used it to achieve several syntheses of natural compounds [6,11,12,13]. He coined the term “resource chemical”, which refers to large-scale and useful substances.…”

Synthesis of a sucrose-based macrocycle with unsymmetrical monosaccharides "arms"

“…Recently, we have prepared sucrose-based macrocyclic derivative 4 in which the terminal positions of this disaccharide (C6 and C6’) are connected via a long polyhydroxylated bridge [ 28 ]. In this model study, both terminal positions in 6,6’-diamino-1’,2,3,3’,4,4’-hexa- O -benzyl-6,6’-dideoxysucrose ( 2 ) were elongated with the same polyhydroxylated unit 1 providing diamide 3 , which subsequently underwent cyclization under the chosen ring-closing metathesis (RCM) conditions [ 29 – 30 ] to give the 21-membered macrocycle 4 ( Scheme 1 ).…”

Multimodule Assembly Strategy for Diverted Total Synthesis and Stereochemical Determination of Laingolide A and Laingolide

“…6,7 This small group of unique macrolides, as depicted in Figure 1, consists of laingolide (1), 8 laingolide A (2), 9,10 laingolide B (3), [11][12][13] palmyrolide A (4), [14][15][16] and madangolide (5). 9 Moreover, the tert-butyl carbinol-containing polyhydroxylated macrolides, such as amantelides A/B, 17 bastimolide A, 18 and nuiapolide, 19 and cyclic depsipeptides, such as apratoxins A/B/E-H 20,21 and janadolide, 22 have been isolated from marine cyanobacteria. Palmyrolide A was isolated in 2010 from a marine cyanobacterial assemblage composed of Leptolyngbya cf.…”