Absolute Stereochemistry of Neohalicholactone from the Brown Alga Laminaria sinclairii

Abstract

Phytochemical analysis of an extract from the brown alga Laminaria sinclairii led to the isolation of neohalicholactone, a cyclopropyl-containing oxylipin previously isolated from a marine sponge, Halichondria okadai. Unequivocal stereochemical analysis of the C-15 hydroxyl group showed this isolate to be of opposite overall absolute stereochemistry compared to that proposed for halicholactone, a related compound from the sponge, and by our inference, sponge-derived neohalicholactone. Comparison of chiroptical data for all three compounds indicates the absolute stereochemistry of the sponge compounds is most probably opposite to that previously proposed.

Natural occurrence, biological activities and synthesis of eight-, nine-, and eleven-membered ring lactones

“…58 Critcher et al reported the synthesis of the right-hand hemisphere 59 and the first asymmetric total synthesis of halicholactone (80) and neohalicholactone (81), 55 confirming the original assignments of absolute configuration of the stereocenters of 81 originally proposed by Yamada and Clardy. 53 They also demonstrated, through the preparation of diastereomers of 81, 55 that the natural product isolated by Proteau et al 54 was, in fact, a C15 epimer of this nine-membered lactone.…”

“…52 In 1991, the relative stereochemistry of all stereocenters of neohalicholactone (81) has been determined by X-ray crystallography as shown below. 53 Some years later, Proteau et al 54 isolated 81 from the brown alga Laminaria sinclairii, and its absolute configuration was suggested to be the opposite to that previously postulated.…”

Epoxy allylic carbocations as conceptual intermediates in the biogenesis of diverse marine oxylipins

“…Subsequently, an X-ray study of neohalicholactone (37) provided relative stereochemistry in this series (57). A potential complication in the structure of halicholactone and neohalicholactone was introduced by isolation and structural description of "neohalicholactone" from the Pacific brown alga L. sinclairii (58). From this kelp we had earlier isolated a variety of 15-1ipoxygenase products, all of which had a 15S stereochemistry (e.g., 15S-HETE, 38, see above) (9).…”

Enantioselective Catalysts for the Synthesis of α‐Substituted Allylboronates—An Accelerated Approach towards Isomerically Pure Homoallylic Alcohols

“…[1,2] Many syntheses rely on the same key reaction, the Nozaki-Hiyama-Kishi reaction [3] starting with vinyl iodides 3 (3a [4] /3b [5] ). Thep resent study led to ag eneral approach towards intermediate 4.…”

“…Z-configured homoallylic alcohols are often found as structural motifs in natural products,f or example in oxylipines such as solandelactone A + B( 1)a nd neohalicholactone (2)a nd related compounds of marine origin (Scheme 1). [1,2] Many syntheses rely on the same key reaction, the Nozaki-Hiyama-Kishi reaction [3] starting with vinyl iodides 3 (3a [4] /3b [5] ). Thep resent study led to ag eneral approach towards intermediate 4.…”