Gram Scale Runs

To a 20 mL flask was added 2.5 g of (R,S)-2-ethoxycarbonyl-3,6-dihydro-2H-pyran, followed by 7 mL of 0.2 M pH 7.5 phosphate buffer and 2 mL of Bacillus lentus protease-III solution (approximately 5% solution of the protein). The biphasic solution was stirred at room temperature (23 °C) using a magnetic stirrer. The pH was checked at 0.5 hour intervals and readjusted to 7.5 by the drop-wise addition of 1 N NaOH (approximately 7 mL were required over the complete reaction). The progress of the reaction was monitored by chiral gas chromatography. After 5 hours, the enantiomeric purity of the unreacted ester was 99% and the reaction was stopped by the addition of 10 mL of MTBE. The pH of the aqueous phase was adjusted to 8.5 and the mixture was transferred into a separatory funnel. The aqueous phase was extracted twice with 20 mL of MTBE and the combined organic layers were extracted once with saturated sodium bicarbonate (10 mL), followed by saturated sodium chloride solution (10 mL), and the organic 

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These studies paved the way for numerous synthetic applications, in particular total syntheses. Thus, the low-tech PtCl2, PtCl4, or PtBr4 systems, as named by Fiirstner, proved superior and more reliable compared to Trost s TCPCtfe system288 for the reactions of the cyclooctene substrate as shown in Scheme 81.300 These reactions, which could be run in a multi-gram scale, proved useful, for instance, for the formal total synthesis of streptorubine B. Similarly, a formal total synthesis of roseophilin was devised, based on a nearly quantitative transformation of an enyne moiety into a bicyclic diene system (Scheme 81).301... 

The mercury-photosensitized dehydrodimerization reaction has been known for nuuiy years, but it has only been made preparatively useful very recently. The key feature of the process is that the system is only active in the vapor phase, so that after condensation the product is protected from further conversion. This implies that the reaction can be run to essentially quantitadve conversion without a fall-off in yield. In order to run on a gram scale to tens of grams, all diat is needed is a quartz flask and a low pressure mercury lamp. Heating the substrate or substrates in the quartz flask with a small drop of mercury leads to smooth formation of the products. Aspects of the process are shown in equations (IS) to (18). 

The hydration of fumaric acid [( )-butenedioic acid, 1 R = H] to (S)-2-hydroxybutanedioic acid (2) is catalyzed by the enzyme fumarase. This reaction can be run even on an industrial scale, exploiting the fumarase activity of immobilized microorganisms77. Unfortunately, the substrate spectrum of fumarase is very narrow. Nevertheless, (Z)-2-chlorobutenedioic acid (3, R = Cl) could be diastereo- and enantioselectively hydrated to (2S,3/ )-2-chloro-3-hydroxybu-tanedioic acid (4) on a 50-gram scale, employing commercially available pig heart fumarase [EC 4.2.1.2.]78. 

TABLE 5 Conditions for Pybrop Activation Gram scale, lab runs... 

That carrying out preparative photochemical reaction in a flow system is preferable to irradiation in batch has been often stated, but not often clearly established. An extensive study demonstrated that the isolated yield and productivity obtained in a batch reactor (immersion well) and in a flow system (a tubing wrapped around low pressure lamps) were essentially identical. The authors concluded that batch is best suited for 10-15 gram scale, while flow reaetors are best suited for a larger seale in a single run (or when a potentially explosive product is formed). 

At last, recycling of the Pd/C catalyst was investigated. Desired product 2-methoxy-3,4-diphenylisoquinolin-l(2hf)-one was obtained in yields of 92, 87, and 85% after the first, second, and third runs, respectively. To further demonstrate the efficiency and practicality of this reaction, a scale-up reaction was performed. Thus, gram-scale synthesis of 2-methoxy-3,4-diphenylisoquinolin-l(2//)-one was achieved in 88% yield. 

Tkble 8-2 shows columns whose diameters have increased from 4.6 to 150 mm, a factor of over thirty times. The loading capacity has increased from a few milligrams per run to several grams per run on the process scale column. The actual loading that can be achieved on a particular size of column will be highly dependant upon the extent of separation of the peak of interest from the peaks of undesired components. If this separation is large the column may be loaded at considerably higher levels than those indicated in Table 8-2. 

Liquefaction - Lab-Scale. 35% DS com starch slurries were liquefied with the CGTase at a dose of 4.46 Phadebas units/gram DS starch at pHs 4.5-5.5 for 14 minutes at 105 C (primary liquefaction) and for 4 hours at 90 (secondary liquefaction) +/- 40 ppm calcium. Final volumes were 5-10 ml. Termamyl and Bacillus stearothermophilus alpha-amylase were run as controls at pHs 6.2 and 5.8, respectively in the presence of 40 ppm calcium. 

The commercial preparation of mercury fulminate is carried out by a process which is essentially the same as that which Howmrd originally recommended. Five hundred or 600 grams of mercury is used for each batch, the operation is practically on the laboratory scale, and several batches are run at the same time. Since the reaction produces considerable frothing, capacious glass balloons are used. The fumes, which are poisonous and inflammable, are passed through condensers, and the condensate, which contains alcohol, acetaldehyde, ethyl nitrate, and ethyl nitrite, is utilized by mixing it with the alcohol for the next batch. 

The allotropes of carbon have very different chemical and physical properties. For example, diamond is the hardest namral substance known. It has a rating of 10 on the Mohs scale. The Mohs scale is a way of expressing the hardness of a material. It runs from 0 (for talc) to 10 (for diamond). The melting point of diamond is about 6,700°F (3,700°C) and its boiling point is about 7,600°F (4,200°C). Its density is 3.50 grams per cubic centimeter. 

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