Rearrangement of (-)-.beta.-Caryophyllene. A Product Analysis and Force Field Study

Abstract

The rearrangement of (-)-/3-caryophyllene (1) with sulfuric acid in ether has been reinvestigated. In the early stage, a multitude of products is formed. Of these, fourteen hydrocarbons (3, 4, 6-17) and four alcohols (5, 18-20) were obtained pure. From the very beginning, the tricycloundecenes 15-17 accumulate quickly. This indicates that a previously unknown rearrangement of 1 by protonation of the exocyclic double bond followed by transannular ring closure is a main reaction, and that the conformation ß is involved. Three hydrocarbons (3, 4, 8) and three alcohols (5,18,19) proved to be stable. They are the main components in the late stage. A complete rearrangement scheme followed from a force field analysis using MMP2. First, all conformations up to 4 kcal above the global minimum of each product and each carbenium ion necessary for its formation were detected automatically using the search program HUNTER. Second, the conformation favoring a specific transformation was searched for. For transannular cyclizations, the conformation with the shortest distance between the atoms to be bound and, for ring openings and 1,2-shifts, the conformation with the smallest dihedral angle between the empty p-orbital and the bond to be broken were selected. In all cases, the selection criteria proved valid: The stereochemistry of the conformations selected matched the stereochemistry of the products observed. On the basis of the results presented, a fully automated search program for favorable rearrangement paths may be developed.

Volatile constituents of the fruit of Garcinia atroviridis and their antibacterial and anti‐inflammatory activities

“… 1 H NMR (400 MHz, CDCl 3 ): δ 0.86 (s, 13‐Me), 0.89 (s, 14‐Me), 1.04 (s, 15‐Me). 13 C NMR (100 MHz, CDCl 3 ): δ 44.7 (s, C‐1), 81.3 (d, C‐2), 47.9 (t, C‐3), 37.4 (s, C‐4), 50.9 (d, C‐5), 19.1 (t, C‐6), 32.0 (t, C‐7), 30.2 (s, C‐8), 33.5 (t, C‐9), 20.8 (t, C‐10), 40.6 (t, C‐11), 43.2 (t, C‐12), 31.7 (q, C‐13), 33.0 (q, C‐14), 25.7 (q, C‐15). Results for the 1 H and 13 C NMR are in good agreement with data reported for this compound Mass spectrometry, m / z %: 222 (M + , 1), 166 (100), 123 (49), 85 (30), 95 (29), 81 (29), 41 (27), 55 (23), 135 (23), 93 (22), 137 (22).…”

“…Results for the 1 H and 13 C NMR are in good agreement with data reported for this compound. [13] Mass spectrometry, m/z %: 222 (M + , 1), 166 (100) 79 (18), in good agreement with literature data for this compound. [16] Micro-dilution Antibacterial Assay The serial dilution technique described by Eloff, using 96-well micro-plates, was employed to determine the minimum inhibitory concentration (MIC) of the total volatiles and the major components of the fruit of G. atroviridis, namely, b-caryophyllene alcohol, ginsenol and (1S,2S,5S,8S)-4,4,8-trimethyltricyclo [6.3.1.0]dodecan-2-ol, for antibacterial activity.…”

“…Commercially, this compound is a fragrance ingredient used in decorative cosmetics, fine fragrances, shampoos, toilet soaps and other toiletries as well as in non‐cosmetic products such as household cleaners and detergents . (−)‐ β ‐Caryopyllene has been proposed as a biogenetic and synthetic precursor of several of the tricyclopentanoid sesquiterpenes, probably formed from rearrangement reactions including trans‐annular cyclizations . In agreement with this view was the detection of compounds such as (1 R ,2 S ,7 S ,9 R )‐2,6,10,10‐tetramethyltricyclo[7.2.0.0 2,7 ]undec‐5‐ene, β ‐panasinsene, (1 S ,2 S ,5 S ,8 S )‐4,4,8‐trimethyltricyclo[6.3.1.0 1,5 ]dodecan‐2‐ol and ginsenol among the volatiles of G. atroviridis fruit.…”

Biomimetic Rearrangements of Complex Terpenoids

“…These results suggested reversible interconversion between intermediates that eventually evolved toward the more stable isomers [21]. This gave experimental support for the results of population predictions based on MM3 calculations, suggesting proportions of 44, 29, and 26% for the αα, βα, and ββ conformers, respectively [24]. At this temperature, the various conformers of caryophyllene (14) are not rapidly interconverting, providing evidence for a significant transition barrier between the αα and ββ conformations.…”

Genetic Dissection of Sesquiterpene Biosynthesis by Fusarium fujikuroi

“…A planar structure with a 4-7-4-skeleton for X was concluded from the H,H COSY and HMBC correlations (Figure 2 A). NMR data have previously been published for three of the 16 possible diastereomers: 5,8-cyclocaryophyllen-4a-ol (16), [25] 5,8-cyclocaryophyllen-4b-ol (17), [25] and koraiol (18) (Figure 2 B). [26] The published NMR data for 18 were incomplete and therefore not useful, whereas comparison of our data to those of 16 and 17 clearly excluded these candidate structures for X.…”