Spectral Modeling and Additive Synthesis

The spectral properties and conformational preferences of some 1 jB -thiadiazole macrocycles have been reported. In connection with thiazoles we find mention of a useful reagent for the spectro-photometric determination of cobalt, 4C labelling of a new B-adrenergic blocking agent, S-596, and synthesis of analogues of the cationic terminus of the antitumour agent Bleomycin A21 . Additionally, a polymer-supported thiazolium salt catalyst, as a model for the thiamine-dependent enzymes, has been prepared, and three 2-alkylbenzothiazole volatile flavour constituents... 

The notion that some components of soimds are well-modeled by sinusoids, while other components are better modeled by spectrally shaped noise, further motivates the residual-excited refinement to the purely sinusoidal additive synthesis model presented in Chapter 4 (Figure 4.4). Using the Fourier transform, we ean inspect the spectrum of a sound and determine whieh... 

In prior chapters we found that spectral shape is important to our perception of sounds, such as vowel/consonant distinctions, the different timbres of the vowels eee and ahh, etc. We also discovered that sinusoids are not the only way to look at modeling the spectra of sounds (or soimd components), and that sometimes just capturing the spectral shape is the most important thing in parametric sound modeling. Chapters 5 and 6 both centered on the notion of additive synthesis, where sinusoids and other components are added to form a final wave that exhibits the desired spectral properties. In this chapter we will develop and refine the notion of subtractive synthesis and discuss techniques and tools for calibrating the parameters of subtractive synthesis to real sounds. The main technique we will use is called Linear Predictive Coding (LPC), which will allow us to automatically fit a low-order resonant filter to the spectral shape of a sound. 

Physical modeling synthesis endeavors to model and solve the physics of sound-producing systems in order to synthesize sound. Unlike sinusoidal additive and modal synthesis (Chapter 4), or PCM sampling synthesis (Chapter 2), both of which can nse one powerM generic model for any sound, physical modeling reqnires a different model for each family of sound producing object. LPC (Chapter 8) is a spectral modeling techniqne, but also has physical interpretations in the one-dimensional ladder implementation. 

The Pherobase database is an extensive compilation of behavior-modifying compounds listed in the various pheromone categories aggregation, alarm, releaser, primer, territorial, trail, sex pheromones, and others. The database contains over 30,000 entries. Jmol images of molecules are shown. The molecules can be projected as either space-filling or wire-frame models. They can be rotated in 3-dimensional space. In addition, the database includes mass spectral, NMR, and synthesis data for more than 2,500 compounds. This is a fun site ... 

As mentioned before structure of 2-2 was proposed by spectral analyses, the position of methylenedioxyl group in isoquinoline of 2-2 is in position C-5—C-6, but it did not exclude its possibility in position C-7—C-8. A total synthesis was accomplished in order to confirm the structure and to derive more samples for pharmacological tests. Piperonal 2-4 was used as starting material. It was oxidized by silver oxide in basic condition to get 2-5, then amidized with dimethyl amine to 2-6 and directed ortho-lithiation with n-butyl-lithium in THF (tetrahydrofuran) to get homogeneous yellow solution, which upon treatment with methyl iodide afforded toluamide 2-7, the yield was 85%. The model synthesis study showed that lithiated toluamide 2-7 could condense with compound 2-14 to achieve the final product 2-2 through several steps (see below). The intermediate compound 2-14 could be synthesized starting from the same piperonal 2-4. It was reacted with cyclohexylamine to get Shiff base 2-8, the latter was reacted with 1.13 equiv. of n-butyllithium at -78°C, the metalated intermediate was carbethoxylated in situ by addition of excess ethyl chloroformate and the aldehyde 2-9 was obtained by extraction with dilute acid. Combination of 2-9 with equimolar of propane-1,3-dithiol a compound 2-10 was obtained, then 2-10 was reduced by lithium aluminum hydride and benzylated with benzyl bromide to 2-12. After treatment with bis(trifluoroacetoxy) iodobenzene, the obtained compound 2-13 was reacted with benzylamine to get the key compound 2-14. 

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