Marine natural products

Effect of Tropical Algae as Additives on Rumen <i>in Vitro</i> Gas Production and Fermentation Characteristics

“…Brown algae produce phlorotannins and a range of other natural products [12,13,40]. This less familiar form of tannins consists of polymers of phloroglucinol units and is exclusive to the brown algae.…”

“…A decrease in gas production throughout the incubation was induced by the red algae compared to positive controls (Figure 1(a)). In variable levels, the red algae contain halogenated compounds, dispersed in several classes of primary and secondary metabolites including indoles, terpenes, acetogenins, phenols, fatty acids and volatile halogenated hydrocarbons [12,13,34]. Red algae have demonstrated activity against a large number of microorganisms [13].…”

“…Both marine and freshwater algae have been used in human nutrition, cosmetics, and pharmaceutical products and have the potential to be used as a supplement for livestock feeds [11]. Secondary metabolites with antimicrobial activity have been identified in green, red and brown algae [12][13][14]. Other species tend to have anti-viral, antioxidant, or anti-inflammatory properties that may be used to manipulate livestock health and productivity.…”

Synthetic approaches toward sesterterpenoids

“…The next task facing the authors was to install a second quaternary stereogenic center in a sterically congested position. Since strategies based on organo cuprate reagents were not successful, the group resorted to a [3,3] sig matropic rearrangement to achieve the desired functionalization. Vinyl ether 131, available in five steps from ketone 130, was heated (160 C) to affect a Claisen rearrangement, giving the desired aldehyde 132 as a single isomer in good yield (65%).…”

“…DHP 3,4 dihydro 2H pyran, PPTS pyr idinium p toluenesulfonate, Saegusa Ito TMS enol ether formation, then Pd(OAc) 2 intermediates in this sequence, it involved a Dieckmann cycli zation that ultimately gave rise to tricyclic ketone 172. An additional four step protocol, including a regio and diaster eoselective reduction of the diketone with LiAl(Ot Bu) 3 H, eventually leading to mesylate 173, the substrate for the key Grob fragmentation reaction. As expected, treating ketone 173 with NaOMe in boiling MeOH resulted in the formation of diester 174, bearing a suitably functionalized eight membered ring.…”