Nuphar Alkaloids and Manifestation of Sulfur

6-Dehydrodeoxynupharidine (42) reacts with electrophilic thiating agents, such as ArSX, resulting in a separable mixture (1 1) of two diastereomeric adducts 43 and 44 (47). The reaction of 42 with p-toluenesulfonyl chloride was studied in detail (48) and products 45-49 identified. The configuration at C-7 was determined by circular dichroism (48). 

Nupharolutine (50) was selectively transformed to A7-dehydronupharolutine (51), a compound prepared for the first time. Treatment of 51 with methyl iodide produced the corresponding methiodide 52, which retained a trans ring junction 

In the last decade more chemical attention has been focused on those Nuphar alkaloids which contain sulfur. The chemical behavior of this group is very much dependent on the presence of sulfur. Sulfur introduces additional steric hindrance to the molecule, creates a new nucleophilic center, and increases the stability of carbanions in sulfoxides the C—S bond in sulfonium salts is strongly polarized. 

The presence of sulfur is manifested strongly in the stereochemical course of the sodium borohydride reduction of Nuphar thiaspirane hemiaminals. This 

The sulfur in a-thioiminium ions interacts more strongly than the sulfur in (3 ions, and experiments show that the introduction of deuterium follows the order C-6axD C-6 axD C-6d, with 70% of incorporation of deuterium. LaLonde s final conclusions are as follows  

---