Secondary Metabolites, Monoterpene–Polyketides Containing a Spiro[3.5]nonane from Cryptocarya laevigata

Abstract

Six novel lactone derivatives, cryptolaevilactones A-F (1-6), were isolated from Cryptocarya laevigata. Their unique spiro[3.5]nonane moiety by hetero [2 + 2] cyclization with monoterpene and polyketide was found for the first time in nature. Structural elucidation using various nuclear magnetic resonance (NMR) techniques revealed that 1-3 and 4-6 are diastereomers and partially established the absolute configurations.

Cryptoyunnanones A–H, Complex Flavanones from Cryptocarya yunnanensis

“…On the other hand, 1 – 4 could be formed by a coupling of obolactone ( 9 ) or 7′,8′-dihydroobolactone ( 10 ) to (2 S /2 R )-5,7-dihydroxyflavanone (Scheme ). Therefore, a C-17 R configuration of 1 – 4 was assigned deductively by comparison of their NMR data with those of 9 and 10 , which was also consistent with most of the reported natural α-pyrones in the genus Cryptocarya displaying the same configurations to date. − There have been only four complex flavanones , and one complex chalcone with similar bicyclic spiroketal skeletons reported before. However, the relative configurations of the three remaining asymmetric carbons at C-11, C-13, and C-15 of these known compounds were not discussed in detail, and their absolute configurations were left undetermined.…”

“…2,26 Accordingly, a 2S absolute configuration for 8 could be assigned by comparison of its NMR data. On the other hand, 1−4 could be formed by a coupling of obolactone (9) or 7′,8′dihydroobolactone (10) to (2S/2R)-5,7-dihydroxyflavanone (Scheme 1). Therefore, a C-17R configuration of 1−4 was assigned deductively by comparison of their NMR data with those of 9 and 10, which was also consistent with most of the reported natural α-pyrones in the genus Cryptocarya displaying the same configurations to date.…”

“…Biogenetic pathways for the formation of 1−8 may be proposed to involve coupling obolactone (9), 7′,8′-dihydroobolactone (10), or cryptobrachytone B ( 11) to (2S/2R)-5,7dihydroxyflavanone, as shown in Scheme 1. Compound 9 or 10 would undergo a reduction and a dehydration to produce intermediate i.…”

“…250 species distributed widely in tropical and subtropical areas throughout the world . Many species of Cryptocarya have been investigated, which has led to the discovery of various natural products mainly including α-pyrones − and alkaloids, − together with complex flavonoids ,− and characteristic flavonoids in the genus Cryptocarya with a hydrogenated A-ring containing a C-5 acetic acid/lactone group. − ,− A wide range of biological activities including antitrypanosomal, antimalarial, cholinesterase inhibitory, antituberculosis, antimicrobial, anti-inflammatory, and especially cytotoxic ,,,− activities have been revealed for many of these compounds.…”

Two Novel Flavonoids and Cytotoxicity Evaluation from Cryptocarya yunnanensis

“…The genus Cryptocarya , family Lauraceae, consists of 200–250 species mainly distributed in the tropical and subtropical areas except Central Africa [1] . Previous phytochemical investigations on some Cryptocarya species have reported a number of α‐pyrones, [2–11] alkaloids [12–15] along with two types of unique flavonoids as complex flavonoids [2,16–20] and cryptocaryanone‐type flavonoids with a dearomative A‐ring containing an acetic acid/lactone unit at C‐5 [3–6,17–23] . Many of these isolates have been revealed with strong cytotoxicity [5,12,15,19–21] together with the other pharmaceutical effects such as anti‐inflammatory, [23] antimalarial, [8] antimicrobial, [20] antitrypanosomal, [4] antituberculosis [18] and cholinesterase inhibitory [13] activities.…”