Of ipsenol

The first compound (37) is clearly a Diels-Alder adduct and was made this way in a synthesis of Ipsenol. ... 

A number of new and asymmetric syntheses of (S)-(-)-ipsenol (34) and (S)-(+)-ipsdienol (35), the pheromone of Ips bark beetles, were reported. Scheme 49 summarizes the synthesis of ipsenol by Riedeker and Steiner [75], which enabled them to prepare 56 g of (S)-34. They employed chiral auxiliary B derived from D-glucose. 

A generous gift of 3-propyl-l,2-dithiolane and of ipsenol was received from D. Wackerchuck (Phero Tech, Inc.). J.H. Borden and L. Chong (Simon Fraser University) contributed a sample of sulcatol. 

Figure 6.13 Examples of the application of normal-phase, radio-HPLC to the analysis of de novo biosynthetic pathways in bark beetles (Scolytidae). Demonstration of sex-specific de novo biosynthesis of ipsenol, ipsdienol, and amitinol through radio-HPLC analysis of pentane extracts of Porapak-trapped volatiles from (A) male and (B) female Ips paraconfusus Lanier feeding for 168 h in Pinus ponderosa and (C) male and (D) female Ips pini (Say) feeding for 168 h in Pinus jeffreyi (Seybold et al., 1995b). Demonstration of sex-specific de novo biosynthesis of frontalin through radio-HPLC analysis of pentane extracts of Porapak-trapped volatiles from (E) male and (F) female...

In other late-stage reactions, studies of the conversion of myrcene and ketone analogues of ipsenol and ipsdienol to the alcohols have been investigated in I. paraconfusus (Fish etal., 1979,1984 Vanderwel, 1991 Ivarsson and Birgersson,... 

Figure 6.15 Hypothetical alternative late stages of enantiospecific de novo biosynthesis of ipsenol and ipsdienol in male Ips paraconfusus and Ips pini. Biosynthesis may proceed from geranyl diphosphate to myrcene as catalyzed by a sex-specific monoterpene synthase. Terpene synthases (including a myrcene synthase) have been characterized from conifers (Bohlmann et al. 1997, 1998). Alternatively, biosynthesis may proceed from geranyl diphosphate to 5-hydroxygeranyl diphosphate (W. Francke, personal communication).

Birch M. C. and Light D. M. (1977) Inhibition of the attractant pheromone response in Ipspini and Ipsparaconfusus (Coleoptera Scolytidae) field evaluation of ipsenol and linalool. J. Chem. Ecol. 3, 257-267. 

The DEPT spectrum of ipsenol is shown in Figure 4.12. It consists of the main spectrum (a), which is a standard -decoupled 13C spectrum the middle spectrum (b) is a DEPT 135 where the CH3 s and CH s are phased up, whereas the CH2 s are phased down. The top spectrum (c) is a DEPT 90, where only CH carbons are detected. Quaternary 13C are not detected in the DEPT subspectra. We can now interpret the 13C peaks in the main spectrum as CH3, CH2, CH, or C by examining the two subspectra peaks along with the main spectrum. The easiest way to approach the interpretation of the 13C/DEPT spectra... 

In this chapter, using these four compounds as examples, we turn our attention to correlation NMR spectrometry most (but not all) of the useful experiments fall into the category of two-dimensional NMR. Our approach in this chapter is to present the spectra for each compound independently as a logical set. Most of the general aspects of each experiment are given in the discussion of ipsenol others are only introduced with the more complicated compounds. The material for ipsenol should be thoroughly covered first. The other compounds can be covered independently or not at all. 

We did a credible job of interpretation of ipsenol using H NMR in Chapter 3, but we can do a better job using correlation methods, quicker and with less ambiguity. Caryophyllene oxide, lactose, and VGSE are, however, too complex to fully analyze using onedimensional H and 13C NMR alone. Before turning our attention to the description of specific experiments and their interpretation, we will first take a closer look at pulse sequences and Fourier transformation. 

Let us begin our discussion of 2-D NMR by considering the H— H COSY spectrum of ipsenol, the monoterpene alcohol considered in some detail in Sections 3.12.1 and 4.6. For reference and as a reminder, the typical 1-D NMR data at 300 MHz for ipsenol and its structure are provided in Figure 5.8. 

Before undertaking detailed discussions of H— H COSY and the structure of ipsenol, there is one further experimental refinement that decreases the clutter along the diagonal. Although we can interpret this spectrum without this refinement, there are instances (i.e., caryophyllene oxide) when this improvement makes a great deal of difference. 

The DQF H— H COSY spectrum of ipsenol can be found at the bottom of Figure 5.9. Note that the spectrum seems cleaner, especially along the diagonal, making the task of interpretation significantly easier. Because of the greatly improved appearance of DQF-COSY, all COSYs in this book are double quantum filtered. 

FIGURE 5.8 300 MHz 1H, l3C, and DEPT spectra for ipsenol in CDC13. The structure of ipsenol is given with the numbering... 

The upper portion in Figure 5.12 is the HETCOR spectrum of ipsenol, and the lower portion is a HMQC spectrum of ipsenol. The presentation of the two spectra is the same except that the axes have... 

FIGURE 5.12 The bottom part of the figure is the HMQC spectrum for ipsenol while the top part of the figure is the HETCOR spectrum of ipsenol. 

Most asymmetric syntheses require rather more than one or two steps from chiral pool constituents. Male bark beetles of the genus Ips produce a pheromone that is a mixture of several enantiomerically pure compounds. One is a simple diene alcohol (S)-(-)-ipsenol. Japanese chemists in the 1970s noted the similarity of part of the structure of ipsenol (in black) to the widely available amino acid (S)-leucine and decided to exploit this in a chiral pool synthesis, using the stereogenic centre (green ring) of leucine to provide the stereogenic centre of ipsenol. 

Isoprenylation. In the presence of TiCU or AICI3, this isoprenylsilane (1) reacts with acid chlorides, acetals, and carbonyl compounds to form isoprenylated compounds. Reactions with the first two electrophiles proceed in higher yield than those with carbonyl compounds. Isoprenylation provides simple syntheses of ipsenol (2) and ipsdienol (3), components of the aggregation pheromone of a bark beetle. 

Brown, H. C., Randad, R. S. B-2 -lsoprenyldiisopinocampheylborane an efficient reagent for the chiral isoprenylation of aldehydes. A convenient route to both enantiomers of ipsenol and ipsdienol. Tetrahedron Lett. 1990, 31,455-458. 

Figure 4.64 Synthesis of the enantiomers of ipsenol (1). Modified by permission of Shokabo Publishing Co., Ltd...

The DQF — H COSY spectrum of ipsenol can be found in Figure 6.11. Note that the spectrum... 

FIGURE 6.11. The 300-MHz DQF-COSY of ipsenol. Compare the diagonal of the DQF-COSY with the diagonal of the simple COSY in Figure 6.9. 

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