Passage
The cryptophycins, isolated from cyanobacteria, are a family of macrocyclic molecules. Researchers have studied the biological activity of these compounds and found that many of them are active against multi-drug-resistant tumor cells.Cryptophycin-52, an analogue of the natural cryptophycins, has been tested in clinical trials for its efficacy against cancer cells, but the studies were suspended due to neurotoxic side effects. Nevertheless, the synthesis of similar analogues continues to be of interest in cancer research. A key step in the synthesis of cryptophycin-52 is the stereospecific formation of an epoxide from an alkene and oxone (Figure 1) , which can be facilitated by the Shi catalyst. The Shi catalyst (Figure 2) is derived from the carbohydrate D-fructose and is known among organic chemists for its ability to form epoxides in hydrocarbons in a stereospecific manner.
Figure 1 Shi epoxidation of compound 1
Figure 2 Structure of the Shi catalystThe epoxidation of compound 1 was monitored by thin-layer chromatography (TLC) . When the reaction was completed, high-performance liquid chromatography (HPLC) was used to analyze the epoxide product. A chiral column that had an affinity for the desired epoxide was used. A standard of the desired epoxide was obtained to optimize the conditions and determine the retention time of the epoxide. The HPLC chromatogram of the epoxide standard is shown in Figure 3.
Figure 3 HPLC of epoxide standard
Adapted from Weiß C, Bogner T, Sammet B, Sewald N. Total synthesis and biological evaluation of fluorinated cryptophycins. Beilstein J Org Chem. 2012.
-The Shi catalyst is derived from D-fructose based on the reaction below. The structure of D-fructose in the form shown below can be classified as: pyranose.furanose.ketohexose.aldohexose.

Question

Passage
The cryptophycins, isolated from cyanobacteria, are a family of macrocyclic molecules. Researchers have studied the biological activity of these compounds and found that many of them are active against multi-drug-resistant tumor cells.Cryptophycin-52, an analogue of the natural cryptophycins, has been tested in clinical trials for its efficacy against cancer cells, but the studies were suspended due to neurotoxic side effects. Nevertheless, the synthesis of similar analogues continues to be of interest in cancer research. A key step in the synthesis of cryptophycin-52 is the stereospecific formation of an epoxide from an alkene and oxone (Figure 1) , which can be facilitated by the Shi catalyst. The Shi catalyst (Figure 2) is derived from the carbohydrate D-fructose and is known among organic chemists for its ability to form epoxides in hydrocarbons in a stereospecific manner.

Figure 1 Shi epoxidation of compound 1

Figure 2 Structure of the Shi catalystThe epoxidation of compound 1 was monitored by thin-layer chromatography (TLC) . When the reaction was completed, high-performance liquid chromatography (HPLC) was used to analyze the epoxide product. A chiral column that had an affinity for the desired epoxide was used. A standard of the desired epoxide was obtained to optimize the conditions and determine the retention time of the epoxide. The HPLC chromatogram of the epoxide standard is shown in Figure 3.

Figure 3 HPLC of epoxide standard
Adapted from Weiß C, Bogner T, Sammet B, Sewald N. Total synthesis and biological evaluation of fluorinated cryptophycins. Beilstein J Org Chem. 2012.
-The Shi catalyst is derived from D-fructose based on the reaction below. The structure of D-fructose in the form shown below can be classified as:

pyranose.furanose.ketohexose.aldohexose.

Quizplus · Accepted Answer

11ecba2d_1261_64e8_a3bf_110d6623f2a8_MD0008_00 Sugars are organic molecules composed of a carbon chain in which one carbon is double-bonded to oxygen and the rest contain a hydroxyl group. They are classified based on several characteristics: the number of carbon atoms they contain, the functional groups in the open chain form, and what type of cyclic structure (if any) they have adopted. Sugar classes are named first for the number of carbon atoms they contain by adding the suffix "-ose" to the Greek prefix corresponding to the carbon number. For example, a five-carbon sugar is a pentose, and a six-carbon sugar is a hexose. The sugar can be further classified as either an aldose or a ketose. An aldose is a sugar that contains an aldehyde functional group with the carbonyl at carbon 1. A ketose contains a ketone, typically at carbon 2. Fructose is a six-carbon sugar with a ketone group, making it a ketohexose (Number III). Some sugars, most commonly pentoses and hexoses, can take on cyclical structures known as pyranoses and furanoses. Pyranoses are six-membered rings and are named due to their similarity to pyran. Furanoses are five-membered rings and are named due to their resemblance to furan. Fructose can be found in either form. The form of D-fructose used to produce the Shi catalyst, as shown in the question, is a six-membered ring. Therefore, it can be classified as a pyranose (Number I). (Number II) Although fructose is most commonly found in the furanose form, this is not the form it takes in the synthesis of the Shi catalyst. (Number IV) Aldohexoses are sugars that contain six carbon atoms in the sugar backbone, as well as an aldehyde functional group. Glucose is an example of an aldohexose. Educational objective: Sugars can be classified by the number of carbon atoms in their backbone, whether they contain an aldehyde or a ketone, and by the cyclic form they adopt. The suffix "-ose" is used to name sugars.

Passage The Cryptophycins, Isolated from Cyanobacteria, Are a Family of Macrocyclic