Synthetic Studies on Stevastelins. 1. Total Synthesis of Stevastelins B and B3

Abstract

[Chemical reaction: See text] The synthesis of stevastelin B3 (2) and B (5) are described. In a first approach, epoxy cyclodepsipeptide 8 was considered as a promising candidate for the synthesis of the [15]-membered ring members of the stevastelins; however, the oxirane ring opening, required for the completion of the natural stevastelin synthesis, failed. Thus, we synthesized stevastelin B (5), carrying out the oxirane ring opening earlier in the synthesis and following a synthetic scheme capable of delivering analogues. On the other hand, a translactonization reaction of the [15]-membered ring derivative 59 led to the total synthesis of the natural [13]-membered ring component of the stevastelins family, stevastelin B3 (2).

Total Synthesis of Amphidinolide J

“…Another fraction consisting of a 4/1 mixture of amphidinolides J and R was also isolated (15%). Interestingly, under similar conditions (rt, 4 h), an acyl shift took place from the 14-membered lactone 25 and amphidinolide J was again isolated as the major product (46%) along with a 1/1 mixture of amphidinolides J and R (18%) (Scheme ). , The spectroscopic data of the isolated pure amphidinolide J were in perfect agreement with those previously reported for the natural product (Δδ ≤ 0.1 ppm in 1 H and 13 C NMR) with a measured optical rotation slightly higher ([α] D +6.7 ( c 0.52, MeOH); lit [α] D +1.2 ( c 0.7, MeOH)).…”

Enantioselective Synthesis Muqubilin and Negombatoperoxides B and C/D

“…Installation of the C-2/C-3 syn aldol moiety was achieved using Evans syn aldol condensation (Scheme ), giving 40 in 94% yield. The chiral auxiliary was then removed by reduction with LiBH 4 . The resulting diol 41 was selectively silylated with TBDPSCl at the primary OH to afford 42 .…”

Polyhydroxyalkanoates – what are the uses? Current challenges and perspectives

“…xvi Sandoval et al, reported that (R)-3-hydroxy-n-phenylalkanoic acid had a significant antimicrobial effect against food pathogen such as Listeria monocytogenes present in the refrigerated food [33]. (R)-3-hydroxy-undecanoate is utilized for synthesis of depsipeptides (antibiotic/antifungal) [34]; lipid A mimic (immunobiological) [35]; (−)-tetrahydrolipstatin (antiobesity drug) [36]. (R)-3-hydroxyhexanoate is used for production of anti-microtubule agent such as analogs of laulimalide [37].…”