Synthesis of rotigotine-2-Azidopropionate

 

¹H NMR (Varian, 500 MHz, 10 mg/mL CDCl₃) showed peaks at 4.203 ppm CH₃CH(N₃)— (q, 1H) and 1.642 ppm CH₃CH(N₃)— (d, 3H).

 https://www.google.com/patents/US8383093

Example 5 Synthesis of rotigotine-2-Azidopropionate

In a 100 mL round bottom flask was placed 2-azidopropionic acid (251 mg, 2.02 mmol, 1.3 equiv.—in 3 mL of DCM), rotigotine (500 mg, 1.55 mmol, 1 equiv.), and 4-DMAP (249 mg, 2.02 mmol, 1.3 equiv.—in 6 mL of DCM) and the mixture was allowed to stir under argon. The solution was cooled by placing the flask in an ice-water bath for 5 min. To the solution, DCC was added (421 mg, 2.02 mmol, 1.3 equiv.). The progress of the reaction was followed by reversed phase HPLC. Following overnight stirring at room temperature, additional 2-azidopropionic acid (126 mg, 0.65 equiv.) in 2 mL of DCM and 4-DMAP (124 mg, 0.65 equiv.) were added to the reaction mixture, followed by DCC (211 mg, 0.65 equiv.). The solution was allowed to stir at room temperature for another 3.5 hours. HPLC result shows 94% of conversion to ester. The reaction mixture was filtered, and the filtrate was concentrated to dryness on a rotary-evaporator. The crude product was then purified by silica gel chromatography. The crude product was dissolved in hexane-ethyl acetate (6 mL, 4:1 v/v), and then loaded on to a 300 mL Silica Gel Column (30 mm id). The column was eluted with a hexane-ethyl acetate (4:1 v/v). The fractions (10 mL each) were analyzed by TLC and reversed phase HPLC. The product fractions were pooled, evaporated by rotary-evaporation, and then dried in vacuum overnight. Yield: 307 mg.

¹H NMR (Varian, 500 MHz, 10 mg/mL CDCl₃) showed peaks at 4.203 ppm CH₃CH(N₃)— (q, 1H) and 1.642 ppm CH₃CH(N₃)— (d, 3H).

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• 10 Great Balinese Fruits

  Top 10 Tropical Fruits To Try In Bali

  
  

  
  

  
  
  
  Fruits in Bali come in a wide variety and are a feast for your eyes and taste buds, with striking and sometimes unusual textures, colours, shapes and sizes. Although several types share much resemblance with those that you find in other places across Southeast Asia, there are some varieties that can only be found here in Bali. This small island eight degrees south of the equator features different terrains that serve as favourable growing places for such fruits. Take the Balinese salak for example, an odd-looking but delicious fruit that is widely grown in the eastern Bali village of Sibetan, Karangasem regency.
  The island’s volcanic highlands allow fertile plains and village plantations to produce a bounty of these exotic and tasty delights. Make most out of your holiday in Bali by pleasing your senses – discover and try as many Balinese fruits as you can. Here is our list of top 10 tropical and exotic fruits to try in Bali. And if you dare, check out how the locals go further with their beloved fruits by adding them as main ingredients in exotic preparations of salads and dishes – you won’t find such an experience elsewhere!
  
  
  
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  Durian

  
  

  Duren
  The fruit most locals love and most foreigners hate. But like the majority of unusual things, it’s an acquired taste. There are three types of people when it comes to the Durian: die-hard lovers, haters, and those in between who love the taste but can’t bear the smell for too long. The powerful aroma has led to the fruit being banned from hotels and airplanes, and locals know that driving some home from a market or roadside stall will have their car reeking of durian for a week! Opening up one of these heavily spiked melon-sized fruits requires much care and experience – a roadside vendor will scan for a faint line to position his blade then easily crack it open to reveal the fleshy white, to deep yellowish pods. The texture and taste: creamy and sweet, means that there is a good reason for durian-flavoured ice cream. The notorious smell: to some, invigorating, sweet, or even okay… and for many others, putrid, rotten, or simply ‘the toilet is broken’! Lovers of blue cheese can try an exchange with the local villagers and get pretty much a very similar response.

  
  

  
  
  
  
  
  
  

  Mangosteen

  
  

  Manggis
  Those who have travelled to other Southeast Asian countries may have already encountered and tried the mangosteen. Pleasant to all, the round, apple-sized and deep purple fruit is easily cracked opened by pressing between both palms, and caution is to be taken as the rind exudes a reddish sap that can stain clothes. The reddish stains on your palms resemble blood at a glance, hence its nickname the ‘blood fruit’. While the white inner flesh is the prize, a recent trend has surfaced in drying up the rinds and making them into health teas, due to its claimed high antioxidant content. Mangosteen is also known in local traditional medicine as a remedy for skin and digestive problems. The juicy flesh sections contain slightly fibrous and inedible seeds, and most will agree that one is never enough. The evergreen trees are largely grown in the highland regions of Tabanan in Bali’s west, and the Bangli regency on the island’s east.

  
  

  
  
  
  
  
  
  

  Salak

  
  

  Snake/Snakeskin Fruit
  This odd-looking fruit deserves its moniker, with skin resembling tiny snake scales from up close. The fruit’s colour ranges from reddish to dark brown, and it grows in clusters on very spiny palm-like trees – not a pleasant or inviting sight. But once harvested and in your hotel room fruit basket, they are smooth and tempting. Oval to round, the fruit has a pointed top that eases squeezing and is peeled by hand. After revealing the three pale yellow lobes, you still need to rub off a thin layer of silky membrane before enjoying the moist and crunchy treat. The largest lobe contains a hard black seed – hazardous to first-timers’ teeth. Texture and taste: sweet and slightly starchy consistency, a cross flavour between pineapple and Royal Gala apples. One type of Bali’s salak has recently been made into wine by farming cooperatives in Karangasem, East Bali. You’ll come across the fruit in almost all traditional markets and supermarkets.

  
  

  
  
  
  
  
  
  

  Rambutan

  
  

  Buluan
  Like the durian, this fruit is straightforwardly named, meaning ‘hairy’ in the local tongue. They grow in clumps on trees that are commonly grown in village backyards in Bali’s rural areas. Green and yellow when young and a bright red when ripe, they reveal a soft and cloudy white flesh with oval seeds. Over a dozen types of salak are available, from long-haired types with very juicy flesh, to dry-looking short-haired ones that are smaller, rounder and with a lesser moist content. You’ll know you are enjoying top-quality rambutan whenever the skin is easily opened; the flesh is sweet and succulent and easily separates from the seed. When buying a bunch from a traditional roadside fruit vendor up in the mountains or at the market, be cautious of black ants that naturally favour the fruit and tree’s sap – they cling on within the leaves and fruit’s hairs even after it is washed.

  
  

  
  
  
  
  
  
  

  Boni

  
  

  Buah Buni
  These are considered wild berries, but can be found in fruit markets and warungs island-wide. Grown on shrub-like trees, the buah buni bear clustering bunches of small and round berries, white, reddish and black in colour. While easily enjoyed as it is, with a taste ranging from biting sour to sweet, the locals are fond of preparing the buni as a rujak or salad mix, with a blend of sugar, chilli, shrimp paste and salt. High in vitamin C, it is also locally known as a remedy for hypertension.

  
  

  
  
  
  
  
  
  

  Soursop

  
  

  Srikaya
  The ‘sour’ in its name is there for clear reason. Soursop is widely grown alongside papayas and bananas in villagers’ backyards, and is a delightful treat during the hot days of summer – often blended with sugar syrup as refreshing drinks. When eaten as it is, its sourness is obvious. Locals look for the fruit whenever they suffer from mouth ulcers. Very soft when ripe, the green skin is easily pinched and peeled away by hand, or sliced with a knife to reveal its aromatic, pulpy and juicy flesh. Enjoying soursop with your hands can be a messy undertaking, best slice open and dig in with a knife and fork, while discarding the small and oval black seeds. A distant cousin to the soursop that you may also find widely sold in Bali’s fruit markets, such as Badung and Kumbasari in Denpasar, is the custard apple, locally known as ‘silik’. Smaller and rounder, the size of an apple, the flesh is similarly tender, but tastes much sweeter.

  
  

  
  
  
  
  
  
  

  Java Plum

  
  

  Juwet
  Similar to the buah buni, the Java Plum is a seasonal fruit, widely grown in the southern Bukit region, and sold in warungs and roadside stalls, and alternatively prepared with a chilli mix. The fruit grows on large trees with dense foliage, and are smooth and shiny, oval-shaped the size of a date. Young green fruit turn pink and then purplish to black when ripe. The taste ranges from sweet to sour. Part of the fun in enjoying Java Plum is, after some bites and chews, you can check your tongue in a mirror – it will be slightly purple. The taste will also linger in your mouth for a while after enjoying even just a little amount. This is perhaps one of the reasons the locals tend to enjoy anything originally sweet and sour with the typical ‘rujak’ mix of shrimp paste, salt, sugar and chilli. You can always ask for a reduction or total omission of the slightly intimidating last ingredient.

  
  

  
  
  
  
  
  
  

  Yellow and Orange Coconut

  
  

  Nyuh Gading
  A widespread but often overlooked fruit: This is not the common green coconut. In Bali, the orange and yellow types are grown for their use in temple and ceremonial purposes. On the culinary side, while much smaller than the common green coconut, the young coconuts of the orange variety offer a much tastier and refreshing treat – the flesh is thinner and tender, and its water is more flavoursome. While not widely sold in tourist areas, you can find them in villages and rural areas where roadside stalls selling flowers usually sell them for ceremonial purposes. If you find a tree bearing these orange coconuts grown in your hotel’s grounds, kindly ask the staff if you can try one. Some hotels in Lovina, North Bali, such as the Puri Saron Baruna Beach Cottage, promote local fruits growing on their property’s premises, which can be a fun experience.

  
  

  
  
  
  
  
  
  

  Ambarella

  
  

  Kedondong
  This tropical fruit grows on low trees, and is green to a lighter colour when ripe. Its flesh is crunchy and a little sour, and is high in vitamin C. Again, it is one of the favourite naturally sour fruits that go with shrimp paste; a sugar, salt and chilli mix, forming a basic ‘rujak kedondong’. The fruit can also be pickled. Preferably peeled and sliced before eaten raw, ambarella contains a spiny seed that you should avoid getting in between your teeth. Warungs (traditional roadside snack stalls) selling rujak will almost always have ambarella among their stock of fruits. Widely available in traditional markets and supermarkets, the locals believe that eating ambarella improves the digestive system and can help cure anaemia.

  
  

  
  
  
  
  
  
  

  Pomelo

  
  

  Jeruk Bali
  A backyard-grown fruit that is also widely sold in traditional markets and supermarkets, this large citrus fruit comes in two general types based on the colour of the flesh, namely white and pink. The rind is thick and spongy, and getting out the lobes in one piece can be a challenge as the small pulps are brittle and break off easily. It is quite juicy after you crunch a mouthful of the pulp, and tastes sweet and sometimes bitter (usually the trait of the pink fleshed varieties). A local belief is that consuming pomelo can cure a hangover. The thick and spongy rinds shouldn’t be wasted – they are burnt to act as a natural mosquito repellent.

 

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