The first total synthesis of (±)-laurokamurene B

Phytochemical and Biological Properties of Sesquiterpene Constituents From the Marine Red Seaweed Laurencia: A Review

“…L. tristicha (Naozhou Island, China) yielded ar-bisabol-9-en-7,11-diol (68) [12]. On the other hand, L. scoparia (S˜ao Paulo, Brazil) was the source of compounds (69)(70)(71). The confirmation of the structure and the absolute configuration of all stereo centers of 69 were proved by single-crystal X-ray crystallography.…”

“…Later on, laurokamurenes A (87) and B (88), were isolated from L. okamurai (Nanji Is., China) [68]. In 2007, total synthesis of the (±)-laurokamurene B (88) was completed, employing a combination of the Ireland-Claisen rearrangement and ring-closing metathesis reactions [69]. Lately, laurokamurene D (89) was isolated from L. okamurai Yamada [61] (Figure 5).…”

Progress in the Chemistry of Organic Natural Products 102

“…Often members of this class are monocyclic (304)(305)(306)(307)(308)(309)(310)(311)(312)(313)(314)(315)(316)(317)(318)(319)(320), but there are also representatives possessing 6,9-epoxy (321-326), 7,10-epoxy (327 and 328), or 7,11-epoxy (329-350) ring systems, the latter of which are commonly known as caespitanes. Nonetheless, up to now there are 72 bisabolanes and related sesquiterpenes (304-375) identified from Laurencia species and their grazers.…”

Why do thioureas and squaramides slow down the Ireland–Claisen rearrangement?

“…Its key step is a [3,3]-sigmatropic rearrangement of a silyl ketene acetal, which is generated in situ by deprotonation of an allyl ester using a strong base [1][2][3]. The products of the Ireland-Claisen rearrangement, γ,δ-unsaturated acids, are useful precursors of biologically active compounds and natural products [4][5][6][7][8][9][10][11]. The ready availability of allylic esters, the ability to control the E/Z geometry of enolates as well as its stereospecificity make this transformation synthetically appealing [12,13].…”