Yams, diosgenin from

Specifically, this describes first the chemistry used to convert diosgenin from Mexican yam roots to dehydropregnenolone and then a discussion of the preparation of pregnenolone from stigmasterol obtained from soybeans. 

Initially, Marker wanted to obtain diosgenin from the roots of the inedible yam Dioscorea mexicana, which grows wild in Mexico (Fig. 6.13). [27] Parke-Davis Co. and other pharmaceutical companies did not want to engage in supply of plant material from Mexico for political and reliability reasons. Thus, Marker quit his position at the Pennsylvania State University in 1943, travelled to Mexico, rented a small house and explored the jungle in the mountains of Veracruz with a mule. 

With the support of Mexican campesinos. Marker eventually harvested some 10 tonnes of yam roots, from which he isolated crude diosgenin as a syrup in a rented laboratory in Mexico City. Once back in the USA, he made an arrangement to generate the product in a friends laboratory for granting a share in the profits. The ultimate yield exceeded 3,000 grams of progesterone, which had a value of some 240,000 US dollars. 

Powdered Dioscorea (wild yam) root or extract is also marketed to treat the symptoms of menopause as an alternative to hormone replacement therapy (see page 279). Although there is a belief that this increases levels of progesterone, which is then used as a biosynthetic precursor of other hormones, there is no evidence that diosgenin is metabolized in the human body to progesterone, and any beneficial effects may arise from diosgenin itself. 

Bile acids were the logical starting point for the manufacture of cortisone in the late 1940s, but steroids from plant sources, and particularly diosgenin ex yams, were gaining credibility as time passed. The chemical synthesis challenges associated with each of these raw materials are outlined in Scheme 7. 

The most viable method for obtaining larger amounts of steroid hormones is to start with some readily available natural product with a structure that is similar to a steroid and convert it to the desired compound. Russell Marker, a professor at Pennsylvania State University, developed such a method to prepare progesterone from diosgenin, a material that is readily available from Mexican yams. His synthesis is outlined in Figure 28.9. However, he could not interest a major pharmaceutical company in his process, so in 1944 he founded his own company, Syntex, in Mexico City to develop it. 

They are also an insect pheromone (grandisol) and defence substance (polyzonimlne), stephanine is an aporphine alkaloid, scytalone a fungal metabolite, and diosgenin is a rare vegetable saponin from Dioscorea, the Mexican yam. It is useful as animal steroids can be made from it (p. 999). 

A large number of steroidal saponins were characterised from the methanol extract of a Taiwanese yam (cultivar Dioscorea pseudojaponica Yamamoto) and characterised by NMR as having various Glc and Rha containing oligosaccharides and the conversions from seroid saponins to diosgenin after acid hydrolysis were found to be around 68 and 90% for furostanol and spirostanol glyco-... 

The limitation of human population growth is among the greatest challenges of our time. To cope with this question, we do not lack the necessary technical means, and natural product chemistry has an important part in this Starting from an extract of yam root, the American chemist Russell Marker created the chemical basis for the development of hormonal contraceptives. Diosgenin was the starting material for the preparation of the first semi-synthetic steroid hormones (cf. Section 6.1). 

The first hormonal contraceptives were prepared by partial synthesis, starting from diosgenin isolated from yam roots. 

An example of a naturally occurring steroid is diosgenin, obtained from root extracts of the Mexican yam and used as a starting material for the synthesis of several commercial steroids. Most striking is the number of rings in the compound. 

Diosgenin, isolated from Mexican yams and used as precursor of progesterone in its semisynthesis as an early oral contraceptive... 

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