The hardest task in designing a retrosynthetic analysis is spotting where to make the disconnections. We shall offer some guidelines to help you, but the best way to learn is through experience and practice. The overall aim of retrosynthetic analysis is to get back to starting materials that are available from chemical suppliers, and to do this as efficiently as possible.

● Guideline 1 Disconnections must correspond to known, reliable reactions.

We have already mentioned that disconnections must correspond to known reliable react ions and it’s the most important thing to bear in mind when working out a retrosynthesis. When we disconnected the ether 2,4-D we chose to disconnect next to the oxygen atom because we know about the synthesis of ethers. We chose not to disconnect on the aryl side of the oxygen atom because we know of no reliable reaction corresponding to nucleophilic attack of an alcohol on an unactivated aromatic ring.

● Guideline 2 For compounds consisting of two parts joined by a heteroatom, disconnect next to the heteroatom.

In all the retrosynthetic analyses you’ve seen so far there is a heteroatom (N or O) joining the rest of the molecule together, and in each case, we made the disconnection next to that N or O. This guideline works for esters, amides, ethers, amines, acetals, sulfides, and so on because these compounds are often made by a substitution reaction. Chlorbenside is used to kill ticks and mites. Using Guideline 2 we can suggest a disconnection next to the sulfur atom; using Guideline 1 we know that we must disconnect on the alkyl and not on the aryl side.

We can now suggest reagents corresponding to the synthons and propose a synthetic scheme.

The next example is the ethyl ester of, and precursor to, cetaben, a drug that can be used to lower blood lipid levels. It is an amine, so we disconnect next to the nitrogen atom.

The alkyl bromide is available but we shall need to make the aromatic amino-ester and the best disconnection for an ester is the C–O bond between the carbonyl group and the esterify ing group.

We have now designed a two-step synthesis of our target molecule, and this is how it is carried out.

اخر الاخبار

اخبار العتبة العباسية المقدسة

جمعية كشافة الكفيل: المجالس الحسينية تعلّم الفتية قيم نهضة الإمام الحسين (عليه السلام)

عَبرَ المجالس الحسينية.. المجمَع العلمي يقدّم محاضرات دينية وتلاوات قرآنية في بغداد والنجف وميسان

برعاية العتبة العباسية المقدسة.. موكب قناديل السماء يُحيي مراسم اليوم الثالث عشر من المحرّم

بعد انتهاء مراسم ذكرى دفن الأجساد الطاهرة قسم رعاية الصحن يباشر بحملة تنظيف واسعة لصحن مرقد أبي الفضل العباس (عليه السلام)

المزيد

الآخبار الصحية

لكبح الجوع وخسارة الوزن.. "سر بسيط" في نظام جوكوفيتش ؟

هل يساعد الرجيم في علاج الأمراض العقلية؟

لحماية أسنان طفلك.. هذا الفيتامين يقلل خطر التسوس

أكل الطعام بسرعة.. طريق سريع إلى أمراض خطيرة

المزيد

الآخبار التكنلوجية

ما هي أفضل درجة حرارة لتكييف الهواء في السيارة؟

ذوبان الأنهار الجليدية يوقظ "عمالقة نائمة"!

9 يوليو يشهد أقصر يوم في التاريخ المسجل ؟!!

راتبه عشرات ملايين الدولارات.. زوكربرغ يخطف "عقل أبل"

المزيد

مواضيع ذات صلة

1,2-Disconnections

Two-group disconnections are better than one-group disconnections

Amine synthesis using functional group interconversions

Functional group interconversion

Multiple step syntheses: avoid chemoselectivity problems

Synthons are idealized reagents

Disconnections must correspond to known, reliable reactions

Synthons are idealized reagents

The E-selective Wittig reaction

The Z-selective Wittig reaction

The Peterson reaction is stereospecific

The one-step Julia olefination